Why does my Mac block certain websites?

My Mac blocks Yahoo and Facebook most of the time. I was told that this is not my router or modem and is a security issue. Why does it only block specific sites? I can't seem to find anything in my security settings.

You're connected on a private and particularly an access-controlled and restricted network, and the administrators of that network have decided that connected users shall not expend available resources and bandwidth with access to various web sites and/or web services.
If the network administrators have established the blocks correctly, you'll need to use fairly advanced techniques to bypass the blocks, and attempts to bypass these blocks — whether the bypasses are successful or not — may well be considered grounds for network disconnection and/or disciplinary action by the organization.
It's common to log these sorts of failures and attempts to bypass, and — given they have control of the switching gear — it can be feasible to uniquely identify the client computer that's making these requests. If not the specific identity of the client computer system or the credentials used, then the location of the client computer that's attempting the connections.
Check with your network administrators, and with the site's policies and procedures.

Similar Messages

Why does firefox grey out certain websites?

<blockquote>Locking duplicate thread.<br>
Please continue here: [[/questions/921487]]</blockquote>
When I go to epicurious.com, website is greyed out and won't function.

Actually, you did post this question a few hours ago here: https://support.mozilla.org/en-US/questions/921487

BEFW11S4-blocks certain websites

I have spent hours w my internet provider trying to identify why certain websites, which were always accessible, all of a sudden can not be accessed wirelessly. After much ado, I connected the modem directly to my laptop and low and behold the websites in question pops up w no problem. Since I am lame when it comes to this stuff, can someone explain to me in plain talk how I can access these websites without having to be tethered to my modem? Is the modem too old, why is it only blocking certain websites? The websites in question are academic and I checked w the institution and all is well at their end. thanks

Well try upgrading the firmware of the router & keep on holding tightly
the reset button in such a way that power light is blinking on the
router & then do a complete network power cycle i.e., unplug the power
cables from the modem & from the router & then plug in the power cable
to the modem first once all the lights are solid green you could plug
in the power cable to the router & check out it will definately work!!

Why does firefox keep blocking websites that I have gone to in the past

Why does firefox keep blocking websites I have gone to in the past?

From http://watchseries.lt/tips#htw
<pre><blockquote>Why videos do not work for me?
You need Flash Player or DivX Player. Both of these programs are used everywhere online; their size is small and will not harm your computer. You should download them from here:
DivX: http://www.divx.com/en/software/download/start
Flash: http://get.adobe.com/flashplayer/</blockquote></pre>

Why does my mac when i try to format my stick say that unable to write to the last block of the device

i bought a new mac with osx lion 10.7.why does my mac when i try to format my transcend 8 gb stick in disk utility say that it is unable to write to the last block of the device?please help me

This may or may not work, but it's worth a try.
Using Disk Utility, try an re-partition the drive into two partitions, making the second partition very small (a megabyte or two), then see if you can format the first partition normally. Leave the second partition alone.
If this works, then the first partiton is what you will use.

Why does my Mac Mini running on Mavericks so slow to start and load apps?

Why does my Mac Mini running on Mavericks take so long to start and load apps?

1. This procedure is a diagnostic test. It changes nothing, for better or worse, and therefore will not, in itself, solve the problem. But with the aid of the test results, the solution may take a few minutes, instead of hours or days.
2. If you don't already have a current backup, back up all data before doing anything else. The backup is necessary on general principle, not because of anything in the test procedure. Backup is always a must, and when you're having any kind of trouble with the computer, you may be at higher than usual risk of losing data, whether you follow these instructions or not.
There are ways to back up a computer that isn't fully functional. Ask if you need guidance.
3. Below are instructions to run a UNIX shell script, a type of program. All it does is to collect information about the state of the computer. That information goes nowhere unless you choose to share it. However, you should be cautious about running any kind of program (not just a shell script) at the behest of a stranger. If you have doubts, search this site for other discussions in which this procedure has been followed without any report of ill effects. If you can't satisfy yourself that the instructions are safe, don't follow them. Ask for other options.
Here's a summary of what you need to do, if you choose to proceed:
☞ Copy a line of text in this window to the Clipboard.
☞ Paste into the window of another application.
☞ Wait for the test to run. It usually takes a few minutes.
☞ Paste the results, which will have been copied automatically, back into a reply on this page.
The sequence is: copy, paste, wait, paste again. You don't need to copy a second time. Details follow.
4. You may have started the computer in "safe" mode. Preferably, these steps should be taken in “normal” mode, under the conditions in which the problem is reproduced. If the system is now in safe mode and works well enough in normal mode to run the test, restart as usual. If you can only test in safe mode, do that.
5. If you have more than one user, and the one affected by the problem is not an administrator, then please run the test twice: once while logged in as the affected user, and once as an administrator. The results may be different. The user that is created automatically on a new computer when you start it for the first time is an administrator. If you can't log in as an administrator, test as the affected user. Most personal Macs have only one user, and in that case this section doesn’t apply. Don't log in as root.
6. The script is a single long line, all of which must be selected. You can accomplish this easily by triple-clicking anywhere in the line. The whole line will highlight, though you may not see all of it in the browser window, and you can then copy it. If you try to select the line by dragging across the part you can see, you won't get all of it.
Triple-click anywhere in the line of text below on this page to select it:
PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/libexec;clear;cd;p=(Software Hardware Memory Diagnostics Power FireWire Thunderbolt USB Fonts 51 4 1000 25 5120 KiB/s 1024 85 \\b%% 20480 1 MB/s 25000 ports 'com.autodesk.AutoCad com.evenflow.dropbox com.google.GoogleDrive' DYLD_INSERT_LIBRARIES\ DYLD_LIBRARY_PATH -86 ` route -n get default|awk '/e:/{print $2}' ` 25 N\\/A down up 102400 25600 recvfrom sendto CFBundleIdentifier 25 25 25 1000 MB );N5=${#p[@]};p[N5]=` networksetup -listnetworkserviceorder|awk ' NR>1 { sub(/^$[0-9]+$ /,"");n=$0;getline;} $NF=="'${p[26]}')" { sub(/.$/,"",$NF);print n;exit;} ' `;f=('\n%s: %s\n' '\n%s\n\n%s\n' '\nRAM details\n%s\n' %s\ %s '%s\n\t(%s)\n' );S0() { echo ' { q=$NF+0;$NF="";u=$(NF-1);$(NF-1)="";gsub(/^ +| +$/,"");if(q>='${p[$1]}') printf("%s (UID %s) is using %s '${p[$2]}'",$0,u,q);} ';};s=(' /^ *$|CSConfigDot/d;s/^ */ /;s/[-0-9A-Fa-f]{22,}/UUID/g;s/(ochat)\.[^.]+(\..+)/\1\2/;/Shared/!s/\/Users\/[^/]+/~/g ' ' s/^ +//;5p;6p;8p;12p;' ' {sub(/^ +/,"")};NR==6;NR==13&&$2<'${p[10]} ' 1s/://;3,6d;/[my].+:/d;s/^ {4}//;H;${ g;s/\n$//;/s: [^EO]|x([^08]|02[^F]|8[^0])/p;} ' ' 5h;6{ H;g;/P/!p;} ' ' ($1~/^Cy/&&$3>'${p[11]}')||($1~/^Cond/&&$2!~/^N/) ' ' /:$/{ N;/:.+:/d;s/ *://;b0'$'\n'' };/^ *(V.+ [0N]|Man).+ /{ s/ 0x.... //;s/[()]//g;s/(.+: )(.+)/ (\2)/;H;};$b0'$'\n'' d;:0'$'\n'' x;s/\n\n//;/Apple[ ,]|Intel|SMSC/d;s/\n.*//;/\)$/p;' ' s/^.*C/C/;H;${ g;/No th|pms/!p;} ' '/= [^GO]/p' '{$1=""};1' ' /Of/!{ s/^.+is |\.//g;p;} ' ' $0&&!/ / { n++;print;} END { if(n<200) print "com.apple.";} ' ' $3~/[0-9]:[0-9]{2}$/ { gsub(/:[0-9:a-f]{14}/,"");} { print|"tail -n'${p[12]}'";} ' ' NR==2&&$4<='${p[13]}' { print $4;} ' ' END { $2/=256;if($2>='${p[15]}') print int($2) } ' ' NR!=13{next};{sub(/[+-]$/,"",$NF)};'"`S0 21 22`" 'NR!=2{next}'"`S0 37 17`" ' NR!=5||$8!~/[RW]/{next};{ $(NF-1)=$1;$NF=int($NF/10000000);for(i=1;i<=3;i++){$i="";$(NF-1-i)="";};};'"`S0 19 20`" 's:^:/:p' '/\.kext\/(Contents\/)?Info\.plist$/p' 's/^.{52}(.+) <.+/\1/p' ' /Launch[AD].+\.plist$/ { n++;print;} END { if(n<200) print "/System/";} ' '/\.xpc\/(Contents\/)?Info\.plist$/p' ' NR>1&&!/0x|\.[0-9]+$|com\.apple\.launchctl\.(Aqua|Background|System)$/ { print $3;} ' ' /\.(framew|lproj)|\):/d;/plist:|:.+(Mach|scrip)/s/:[^:]+//p ' '/root/p' ' !/\/Contents\/.+\/Contents|Applic|Autom|Frameworks/&&/Lib.+\/Info.plist$/ { n++;print;} END { if(n<1000) print "/System/";} ' '/^\/usr\/lib\/.+dylib$/p' ' /Temp|emac/d;/(etc|Preferences)\//s/^\.\/[^/]+//p;' ' /\/(Contents\/.+\/Contents|Frameworks)\/|\.wdgt\/.+\.([bw]|plu)/d;p;' 's/\/(Contents\/)?Info.plist$//;p' ' { gsub("^| ","||kMDItem'${p[35]}'=");sub("^.."," ") };1 ' p '{print $3"\t"$1}' 's/\'$'\t''.+//p' 's/1/On/p' '/Prox.+: [^0]/p' '$2>'${p[9]}'{$2=$2-1;print}' ' BEGIN { i="'${p[26]}'";M1='${p[16]}';M2='${p[18]}';M3='${p[31]}';M4='${p[32]}';} !/^A/ { next;} /%/ { getline;if($5<M1) a="user "$2"%, system "$4"%";} /disk0/&&$4>M2 { b=$3" ops/s, "$4" blocks/s";} $2==i { if(c) { d=$3+$4+$5+$6;next;};if($4>M3||$6>M4) c=int($4/1024)" in, "int($6/1024)" out";} END { if(a) print "CPU: "a;if(b) print "I/O: "b;if(c) print "Net: "c" (KiB/s)";if(d) print "Net errors: "d" packets/s";} ' ' /r\[0\] /&&$NF!~/^1(0|72\.(1[6-9]|2[0-9]|3[0-1])|92\.168)\./ { print $NF;exit;} ' ' !/^T/ { printf "(static)";exit;} ' '/apsd|OpenD/!s/:.+//p' ' (/k:/&&$3!~/(255\.){3}0/ )||(/v6:/&&$2!~/A/ ) ' ' $1~"lR"&&$2<='${p[25]}';$1~"li"&&$3!~"wpa2";' ' BEGIN { FS=":";} { n=split($3,a,".");sub(/_2[01].+/,"",$3);print $2" "$3" "a[n]" "$1;b=b$1;} END { if(b) print("\n\t* Code injection");} ' ' NR!=4{next} {$NF/=10240} '"`S0 27 14`" ' END { if($3~/[0-9]/)print$3;} ' ' BEGIN { L='${p[36]}';} !/^[[:space:]]*(#.*)?$/ { l++;if(l<=L) f=f"\n "$0;} END { F=FILENAME;if(!F) exit;if(!f) f="\n [N/A]";"file -b "F|getline T;if(T!~/^(AS.+ (En.+ )?text$|POSIX sh.+ text ex)/) F=F" ("T")";printf("\nContents of %s\n%s\n",F,f);if(l>L) printf("\n ...and %s more line(s)\n",l-L);} ' ' BEGIN{FS="= "} /Path/{print $2} ' ' /^ +B/{ s/.+= |(-[0-9]+)?\.s.+//g;p;} ' ' END{print NR} ' ' /id: N|te: Y/{i++} END{print i} ' ' / /{$0="'"${p[28]}"'"};1;' '/ en/!s/\.//p' ' NR!=13{next};{sub(/[+-M]$/,"",$NF)};'"`S0 39 40`" ' $10~/$L/&&$9!~"localhost" { sub(/.+:/,"",$9);print $1": "$9;} ' '/^ +r/s/.+"(.+)".+/\1/p' 's/(.+\.wdgt)\/(Contents\/)?Info\.plist$/\1/p' 's/^.+\/(.+)\.wdgt$/\1/p' );c1=(system_profiler pmset\ -g nvram fdesetup find syslog df vm_stat sar ps sudo\ crontab sudo\ iotop top pkgutil PlistBuddy whoami cksum kextstat launchctl sudo\ launchctl crontab 'sudo defaults read' stat lsbom mdfind ' for i in ${p[24]};do ${c1[18]} ${c2[27]} $i;done;' defaults\ read scutil sudo\ dtrace sudo\ profiles sed\ -En awk /S*/*/P*/*/*/C*/*/airport networksetup mdutil sudo\ lsof test );c2=(com.apple.loginwindow\ LoginHook '-c Print /L*/P*/loginw*' '-c Print L*/P*/*loginit*' '-c Print L*/Saf*/*/E*.plist' '~ $TMPDIR.. \( -flags +sappnd,schg,uappnd,uchg -o ! -user $UID -o ! -perm -600 $' '.??* -path .Trash -prune -o -type d -name *.app -print -prune' '-c Print\ :'${p[35]}' 2>&1' '-c Print\ :Label 2>&1' '{/,}L*/{Con,Pref}* -type f ! -size 0 -name *.plist -exec plutil -s {} \;' "-f'%N: %l' Desktop L*/Keyc*" therm sysload boot-args status " -F '\$Time \$Message' -k Sender kernel -k Message Req 'Beac|caug|dead[^bl]|FAIL|GPU |hfs: Ru|inval|jnl:|last value [1-9]|n Cause: -|NVDA$|pagin|proc: t|Roamed|rror|ssert|Thrott|tim(ed? ?|ing )o|WARN' -k Message Rne 'Goog|ksadm|SMC:' -o -k Sender fseventsd -k Message Req 'SL' " '-du -n DEV -n EDEV 1 10' 'acrx -o comm,ruid,%cpu' '-t1 10 1' '-f -pfc /var/db/r*/com.apple.*.{BS,Bas,Es,OSXU,Rem,up}*.bom' '{/,}L*/Lo*/Diag* -type f -regex .\*[cgh] ! -name *ag \( -exec grep -lq "^Thread c" {} \; -exec printf \* \; -o -true $ -execdir stat -f:%Sc:%N -t%F {} \;|sort -t: -k2 |tail -n'${p[38]} '-L {/{S*/,},}L*/Lau* -type f' '-L /{S*/,}L*/StartupItems -type f -exec file {} +' '-L /S*/L*/{C*/Sec*A,E}* {/,}L*/{A*d,Ca*/*/Ex,Compon,Ex,In,iTu,Keyb,Mail/B,P*P,Qu*T,Scripti,Sec,Servi,Spo,Widg}* -type f -name Info.plist' '/usr/lib -type f -name *.dylib' `awk "${s[31]}"<<<${p[23]}` "/e*/{auto,{cron,fs}tab,hosts,[lps]*.conf,pam.d,ssh{,d}_config,*.local} {,/usr/local}/etc/periodic/*/* /L*/P*{,/*}/com.a*.{Bo,sec*.ap}* .launchd.conf" list getenv /Library/Preferences/com.apple.alf\ globalstate --proxy '-n get default' -I --dns -getdnsservers -getinfo\ "${p[N5]}" -P -m\ / '' -n1 '-R -l1 -n1 -o prt -stats command,uid,prt' '--regexp --only-files --files com.apple.pkg.*|sort|uniq' -kl -l -s\ / '-R -l1 -n1 -o mem -stats command,uid,mem' -i4TCP:0-1023 com.apple.dashboard\ layer-gadgets '-d /L*/Mana*/$USER&&echo On' );N1=${#c2[@]};for j in {0..8};do c2[N1+j]=SP${p[j]}DataType;done;N2=${#c2[@]};for j in 0 1;do c2[N2+j]="-n ' syscall::'${p[33+j]}':return { @out[execname,uid]=sum(arg0) } tick-10sec { trunc(@out,1);exit(0);} '";done;l=(Restricted\ files Hidden\ apps 'Elapsed time (s)' POST Battery Safari\ extensions Bad\ plists 'High file counts' User Heat System\ load boot\ args FileVault Diagnostic\ reports Log 'Free space (MiB)' 'Swap (MiB)' Activity 'CPU per process' Login\ hook 'I/O per process' Mach\ ports kexts Daemons Agents launchd Startup\ items Admin\ access Root\ access Bundles dylibs Apps Font\ issues Inserted\ dylibs Firewall Proxies DNS TCP/IP Wi-Fi Profiles Root\ crontab User\ crontab 'Global login items' 'User login items' Spotlight Memory Listeners Widgets Parental\ Controls );N3=${#l[@]};for i in 0 1 2;do l[N3+i]=${p[5+i]};done;N4=${#l[@]};for j in 0 1;do l[N4+j]="Current ${p[29+j]}stream data";done;A0() { id -G|grep -qw 80;v[1]=$?;((v[1]==0))&&sudo true;v[2]=$?;v[3]=`date +%s`;clear >&-;date '+Start time: %T %D%n';};for i in 0 1;do eval ' A'$((1+i))'() { v=` eval "${c1[$1]} ${c2[$2]}"|'${c1[30+i]}' "${s[$3]}" `;[[ "$v" ]];};A'$((3+i))'() { v=` while read i;do [[ "$i" ]]&&eval "${c1[$1]} ${c2[$2]}" \"$i\"|'${c1[30+i]}' "${s[$3]}";done<<<"${v[$4]}" `;[[ "$v" ]];};A'$((5+i))'() { v=` while read i;do '${c1[30+i]}' "${s[$1]}" "$i";done<<<"${v[$2]}" `;[[ "$v" ]];};';done;A7(){ v=$((`date +%s`-v[3]));};B2(){ v[$1]="$v";};for i in 0 1;do eval ' B'$i'() { v=;((v['$((i+1))']==0))||{ v=No;false;};};B'$((3+i))'() { v[$2]=`'${c1[30+i]}' "${s[$3]}"<<<"${v[$1]}"`;} ';done;B5(){ v[$1]="${v[$1]}"$'\n'"${v[$2]}";};B6() { v=` paste -d: <(printf "${v[$1]}") <(printf "${v[$2]}")|awk -F: ' {printf("'"${f[$3]}"'",$1,$2)} ' `;};B7(){ v=`grep -Fv "${v[$1]}"<<<"$v"`;};C0(){ [[ "$v" ]]&&echo "$v";};C1() { [[ "$v" ]]&&printf "${f[$1]}" "${l[$2]}" "$v";};C2() { v=`echo $v`;[[ "$v" != 0 ]]&&C1 0 $1;};C3() { v=`sed -E "$s"<<<"$v"`&&C1 1 $1;};for i in 1 2;do for j in 2 3;do eval D$i$j'(){ A'$i' $1 $2 $3; C'$j' $4;};';done;done;{ A0;A2 0 $((N1+1)) 2;C0;A1 0 $N1 1;C0;B0;C2 27;B0&&! B1&&C2 28;D12 15 37 25 8;A1 0 $((N1+2)) 3;C0;D13 0 $((N1+3)) 4 3;D23 0 $((N1+4)) 5 4;for i in 0 1 2;do D13 0 $((N1+5+i)) 6 $((N3+i));done;D13 1 10 7 9;D13 1 11 8 10;D22 2 12 9 11;D12 3 13 10 12;D23 4 19 44 13;D23 5 14 12 14;D22 6 36 13 15;D22 7 37 14 16;D23 8 15 38 17;D22 9 16 16 18;B1&&{ D22 11 17 17 20;for i in 0 1;do D22 28 $((N2+i)) 45 $((N4+i));done;};D22 12 44 54 45;D22 12 39 15 21;A1 13 40 18;B2 4;B3 4 0 19;A3 14 6 32 0;B4 0 5 11;A1 17 41 20;B7 5;C3 22;B4 4 6 21;A3 14 7 32 6;B4 0 7 11;B3 4 0 22;A3 14 6 32 0;B4 0 8 11;B5 7 8;B1&&{ A2 19 26 23;B7 7;C3 23;};A2 18 26 23;B7 7;C3 24;A2 4 20 21;B7 6;B2 9;A4 14 7 52 9;B2 10;B6 9 10 4;C3 25;D13 4 21 24 26;B4 4 12 26;B3 4 13 27;A1 4 22 29;B7 12;B2 14;A4 14 6 52 14;B2 15;B6 14 15 4;B3 0 0 30;C3 29;A1 4 23 27;B7 13;C3 30;D13 24 24 32 31;D13 25 37 32 33;A1 23 18 28;B2 16;A2 16 25 33;B7 16;B3 0 0 34;B2 21;A6 47 21&&C0;B1&&{ D13 21 0 32 19;D13 10 42 32 40;D22 29 35 46 39;};D23 14 1 48 42;D12 34 43 53 44;D22 0 $((N1+8)) 51 32;D13 4 8 41 6;D12 26 28 35 34;D13 27 29 36 35;A2 27 32 39&&{ B2 19;A2 33 33 40;B2 20;B6 19 20 3;};C2 36;D23 33 34 42 37;B1&&D23 35 45 55 46;D23 32 31 43 38;D12 36 47 32 48;D13 20 42 32 41;D23 14 2 48 43;D13 4 5 32 1;D22 4 4 50 0;D13 14 3 49 5;B3 4 22 57;A1 26 46 56;B7 22;B3 0 0 58;C3 47;D23 22 9 37 7;A7;C2 2;} 2>/dev/null|pbcopy;exit 2>&-
Copy the selected text to the Clipboard by pressing the key combination command-C.
7. Launch the built-in Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Click anywhere in the Terminal window and paste by pressing command-V. The text you pasted should vanish immediately. If it doesn't, press the return key.
8. If you see an error message in the Terminal window such as "syntax error," enter
exec bash
and press return. Then paste the script again.
9. If you're logged in as an administrator, you'll be prompted for your login password. Nothing will be displayed when you type it. You will not see the usual dots in place of typed characters. Make sure caps lock is off. Type carefully and then press return. You may get a one-time warning to be careful. If you make three failed attempts to enter the password, the test will run anyway, but it will produce less information. In most cases, the difference is not important. If you don't know the password, or if you prefer not to enter it, press the key combination control-C or just press return three times at the password prompt. Again, the script will still run.
If you're not logged in as an administrator, you won't be prompted for a password. The test will still run. It just won't do anything that requires administrator privileges.
10. The test may take a few minutes to run, depending on how many files you have and the speed of the computer. A computer that's abnormally slow may take longer to run the test. While it's running, there will be nothing in the Terminal window and no indication of progress. Wait for the line
[Process completed]
to appear. If you don't see it within half an hour or so, the test probably won't complete in a reasonable time. In that case, close the Terminal window and report the results. No harm will be done.
11. When the test is complete, quit Terminal. The results will have been copied to the Clipboard automatically. They are not shown in the Terminal window. Please don't copy anything from there. All you have to do is start a reply to this comment and then paste by pressing command-V again.
At the top of the results, there will be a line that begins with "Model Identifier." If you don't see that, but instead see a mass of gibberish, you didn't wait for the "Process completed" message to appear in the Terminal window. Please wait for it and try again.
If any private information, such as your name or email address, appears in the results, anonymize it before posting. Usually that won't be necessary.
12. When you post the results, you might see the message, "You have included content in your post that is not permitted." It means that the forum software has misidentified something in the post as a violation of the rules. If that happens, please post the test results on Pastebin, then post a link here to the page you created.
Note: This is a public forum, and others may give you advice based on the results of the test. They speak only for themselves, and I don't necessarily agree with them.
Copyright © 2014 by Linc Davis. As the sole author of this work, I reserve all rights to it except as provided in the Use Agreement for the Apple Support Communities website ("ASC"). Readers of ASC may copy it for their own personal use. Neither the whole nor any part may be redistributed.

Why does my Mac Book pro keep restarting

why does my Mac Book pro keep restarting and how can it be fixed

It would be nice if you could include a kernel panic log to verify that your problem is...
Mid-2010 15" MacBook Pros - the bad NVIDIA GPU
If you're having frequent kernel panics with your 15" mid-2010, or intermittent screen problems, the problem is, more than likely, the faulty NVIDIA GPU found in a number of those machines.
Here's just a sample of a kernel panic log that points to the faulty NVIDIA card:
Kernel Extensions in backtrace (with dependencies):
         com.apple.GeForce(6.4.0)@0x82ac4000->0x82b7afff
            dependency: com.apple.NVDAResman(6.4.0)@0x834a0000
            dependency: com.apple.iokit.IONDRVSupport(2.2.1)@0x82fd3000
            dependency: com.apple.iokit.IOPCIFamily(2.6.5)@0x7a802000
            dependency: com.apple.iokit.IOGraphicsFamily(2.2.1)@0x8301b000
         com.apple.nvidia.nv50hal(6.4.0)@0x83c05000->0x84019fff
            dependency: com.apple.NVDAResman(6.4.0)@0x834a0000
         com.apple.NVDAResman(6.4.0)@0x834a0000->0x8378dfff
            dependency: com.apple.iokit.IOPCIFamily(2.6.5)@0x7a802000
            dependency: com.apple.iokit.IONDRVSupport(2.2.1)@0x82fd3000
            dependency: com.apple.iokit.IOGraphicsFamily(2.2.1)@0x8301b000
Here's the "official" Apple take on the issue - but the very real kernel panics need not be preceded by 'Intermittent black screen or loss of video'... in fact, you might not experience any video problems at all. Although video problems can certainly be a portent of things to come…
So what can you do? Print out a copy of your kernel panic and a copy of the Knowledge Base article and take them, along with your machine, to your local Apple Store or an Apple Authorized Service Provider. The unfortunate thing is that many people have passed the “three years from date of purchase” now and Apple is not honoring the free logic board replacement for many users. Some dealers seem to be making some exceptions for those past the three year mark, but don’t count on it…
Good luck,
Clinton

Why does my Mac stay on the white screen when I turn it on?

Why does my Mac stay on white screen when I turn it on?

Take each of these steps that you haven't already tried. Stop when the problem is resolved.
Step 1
The first step in dealing with a boot failure is to secure your data. If you want to preserve the contents of the startup drive, and you don't already have at least one current backup, you must try to back up now, before you do anything else. It may or may not be possible. If you don't care about the data that has changed since your last backup, you can skip this step.
There are several ways to back up a Mac that is unable to boot. You need an external hard drive to hold the backup data.
a. Boot into the Recovery partition, or from a local Time Machine backup volume (option key at startup.) When the OS X Utilities screen appears, launch Disk Utility and follow the instructions in this support article, under “Instructions for backing up to an external hard disk via Disk Utility.”
b. If you have access to a working Mac, and both it and the non-working Mac have FireWire or Thunderbolt ports, boot the non-working Mac in target disk mode. Use the working Mac to copy the data to another drive. This technique won't work with USB, Ethernet, Wi-Fi, or Bluetooth.
c. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.
Step 2
Sometimes a boot failure can be resolved by resetting the NVRAM.
Step 3
If there's a built-in optical drive, a disc may be stuck in it. Follow these instructions to eject it.
Step 4
Press and hold the power button until the power shuts off. Disconnect all wired peripherals except those needed to boot, and remove all aftermarket expansion cards. Use a different keyboard and/or mouse, if those devices are wired. If you can boot now, one of the devices you disconnected, or a combination of them, is causing the problem. Finding out which one is a process of elimination.
If you've booted from an external storage device, make sure that your internal boot volume is selected in the Startup Disk pane of System Preferences.
Step 5
Boot in safe mode. Note: If FileVault is enabled on some models, or if a firmware password is set, or if the boot volume is a software RAID, you can’t do this. Post for further instructions.
Safe mode is much slower to boot and run than normal, and some things won’t work at all, including wireless networking on certain Macs.
The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.
When you boot in safe mode, it's normal to see a dark gray progress bar on a light gray background. If the progress bar gets stuck for more than a few minutes, or if the system shuts down automatically while the progress bar is displayed, your boot volume is corrupt and the drive is probably malfunctioning. In that case, go to Step 6.
If you can boot and log in now, empty the Trash, and then open the Finder Info window on your boot volume ("Macintosh HD," unless you gave it a different name.) Check that you have at least 9 GB of available space, as shown in the window. If you don't, copy as many files as necessary to another volume (not another folder on the same volume) and delete the originals. Deletion isn't complete until you empty the Trash again. Do this until the available space is more than 9 GB. Then reboot as usual (i.e., not in safe mode.)
If the boot process hangs again, the problem is likely caused by a third-party system modification that you installed. Post for further instructions.
Step 6
Launch Disk Utility in Recovery mode (see Step 1.) Select your startup volume, then run Repair Disk. If any problems are found, repeat until clear. If Disk Utility reports that the volume can't be repaired, the drive has malfunctioned and should be replaced. You might choose to tolerate one such malfunction in the life of the drive. In that case, erase the volume and restore from a backup. If the same thing ever happens again, replace the drive immediately.
This is one of the rare situations in which you should also run Repair Permissions, ignoring the false warnings it may produce. Look for the line "Permissions repair complete" at the end of the output. Then reboot as usual.
Step 7
Reinstall the OS. If your Mac was upgraded from an older version of OS X, you’ll need the Apple ID and password you used to upgrade.
Step 8
Repeat Step 6, but this time erase the boot volume in Disk Utility before installing. The system should automatically reboot into the Setup Assistant. Follow the prompts to transfer your data from a Time Machine or other backup.
Step 9
This step applies only to older Macs (not current models) that have a logic-board ("PRAM") battery. Both desktop and portable Macs used to have such a battery. The logic-board battery, if there is one, is separate from the main battery of a portable. A dead logic-board battery can cause a boot failure. Typically the failure will be preceded by loss of the settings for the startup disk and system clock. See the user manual for replacement instructions. You may have to take the machine to a service provider to have the battery replaced.
Step 10
If you get this far, you're probably dealing with a hardware fault. Make a "Genius" appointment at an Apple Store, or go to another authorized service provider.

Why does Firefox always block any link I try to open going to a web page when I don't have pop up blocker on?

Why does Firefox always block any link I try to open going to a web page when I don't have pop up blocker on? First off they are not even pop ups....your crap blocks everything and don't save user names &/or passwords when you have it checked. Also in your tutorials about solving this issue says it has the word "OPTION" .......no, it never says option to allow you to bypass it and etc. Only thing is says is "ALLOW" . That would be nice , but the problem is it will not allow it from then on. It only allows it right then and then you have to refresh...after that to open again it blocks it again.....HOW STUPID?!!!!!
It always say that this is preventing this page from automatically redirecting to another page. THIS IS WHAT I AM TRYING TO DO...GO TO ANOTHER PAGE........I DON'T NEED YOUr BROWSERS PERMISSION TO DO THAT. THAT IS WHAT A *%#$&*(&*%$$%% BROWSER IS FOR TO GO TO OTHER PAGES......THEY ARE NOT POP UPS!!!!!
YOU STUPID BROWSER ACTUALLY BLOCKS EVERYTHING AND THAT SUX!!!
HELP!!

Are you using "Clear history when Firefox closes"?
In case you are using "Clear history when Firefox closes":
*do not clear the Cookies
*do not clear the Site Preferences
*Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
*https://support.mozilla.org/kb/Clear+Recent+History
Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords.
Clearing cookies will remove all specified (selected) cookies including cookies with an allow exception that you want to keep.
Let all cookies expire when you close Firefox.
*Firefox/Tools > Options > Privacy > Cookies: Keep until: I close Firefox
You can choose to keep third-party cookies from visited sites if necessary.
Create a cookie 'allow' exception for cookies that you want to keep.
*Firefox/Tools > Options > Privacy > Cookies: Exceptions

Why does my mac reboot on its own?

Why does my mac reboot on its own?

Oh den.thed... I saw your post this morning and I was so excited.... ran to the Mac and got to Energy Saver, and... the checkbox is already unchecked.
Long story, I'll make it short. Just got the Mac back after having the HDD replaced. (It stopped working after less than 500 hours.) This rebooting thing has been happening ever since I got the computer in 2010, and I was hoping it would coincidentally stop happening after having this crashed HDD replaced last week. No such luck. Still doing it, even after getting the computer back from Apple. Two of my kids have macbooks, have used the cr*p out of them, and have had very few problems (nothing big). I bought this Mac, to replace a dead Dell desktop that got very little use, and so far I am not sure I did the right thing. Really wish I could get this "automatic" rebooting thing fixed. (Reboots with no notice, while doing normal tasks - internet, word docs, etc.) Thanks again for your help. Let me know if I should try anything else.

Why does my Mac Book go to a presenters mode when I connect to a projector?

Why does my Mac go into a presenters mode when connected to a projector or system?

But does it then come fully awake? My MB Pro comes on with out of focus screen as if in a fog but once it comes awake it clears up, there is a progress bar at the bottom showing the progress from sleep

Why does my mac mini getting hot

why does my mac mini get hot and run fan speeds up high. I've added ram and do not understand the temperature flucuations.

How hot is hot? What programs are you running when it gets hot?

I want to block certain websites

While I am having problems with facebook and loads of unwanted ads, is there any way I can permanently block certain websites or ads from Firefox?

Having a '''hosts''' file on Windows systems, and in Firefox use of the '''Adblock Plus''' extension with subscriptions are two major methods of blocking sites and/or files. With Adblock Plus you can block advertisements without blocking the site itself.
* Blocking bad sites and annoyances - MozillaZine Knowledge Base<br>http://kb.mozillazine.org/Blocking_bad_sites_and_annoyances

Why does Safari say "Blocked Plug-in" when I want a video?

Why does Safari say "Blocked Plug-in" when I want a video?

When you have installed the latest version of Flash, relaunch Safari and test.
If you're getting a "blocked plug-in" error, then in System Preferences… ▹ Flash Player ▹ Advanced
click Check Now. Quit and relaunch your browser.

WHY DOES MY MAC BOOK PRO SHUT OFF ON ME? SO FAR THE INFO I GOT 4 IT IS A MAC OS X VERSION 10.7.3 THE PROCESSOR IS 2.4 GHZ INTEL CORE 2 DUO MEMORY IS 2 GB 667MHZ DDR2 SDRAM I DON'T KNOW HOW OLD IT IS BECAUSE I BOUGHT IT USED SORRY I HOPE THIS HELPS THANK Y

WHY DOES MY MAC BOOK PRO SHUT OFF ON ME? SO FAR THE INFO I GOT 4 IT IS A MAC OS X VERSION 10.7.3 THE PROCESSOR IS 2.4 GHZ INTEL CORE 2 DUO MEMORY IS 2 GB 667MHZ DDR2 SDRAM I DON'T KNOW HOW OLD IT IS BECAUSE I BOUGHT IT USED SORRY I HOPE THIS HELPS THANK YOU

Sounds to me like you may have gotten a machine with hardware issues, but it's hard to say. It will shut down if it gets too hot, but that's not a normal occurrence. I have never seen a MacBook Pro shut down due to heat, even after lengthy 3D gaming sessions where the fans are running fast and the bottom of the machine is unpleasant to touch.
First thing I would try to do is reset the SMC. If that doesn't help, erase the hard drive and reinstall the system from scratch, which you should always do with a used machine anyway.
If a fresh system doesn't help, you'll need to get it checked out by Apple.
Edit: Oh, and sig is absolutely right... please don't post in all caps! It's very irritating.

Why does my Mac block certain websites?

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