EDITING HOSTS - Why I do not find the file on MacBookPro

Question

I am not so expert with Unix.
I edited my Hosts file adding text from http://www.mvps.org/winhelp2002/hosts.htm and it works well on my iMac greatly reduceing the unwanted popups.
Now I try to do the same on my MacBookPro but it seems impossible to find the Hosts file and even Private and etc folders... any suggestion ??
Second question: which is the risk of a wrong editing ? I always keep a copy of the original Hosts file. If there is even the risk of boot made impossible it should always be possible to enter the HD from a second Mac via FW and change the Hosts file or am I wrong ?
Thanks

Answer 1

I edited my Hosts file adding text from http://www.mvps.org/winhelp2002/hosts.htm and it works well on my iMac greatly reduceing the unwanted popups.
I've found the worst pop-up offender is Flash.
I would suggest trying "ClickToFlash" <http://clicktoflash.com/> on Safari.
FlashBlock <http://flashblock.mozdev.org/> for Firefox.
Actually FlashBlock exists for several browsers (Google is your friend).
A Flash blocking add-on will still allow you to play Flash, you just have to click on the blank image with the Start Icon before the add-on will load the Flash content.
As an added bonus, keeping Flash from running by default has a tendency to extend your laptop battery time between charges.
After blocking Flash, the browsers built-in pop-up blockers should get most of the rest, and if there is a really offensive Ad, you can also use an Ad blocking add-on as mentioned by etresoft. I use one of those as well, but ever since I installed a Flash blocking add-on, I have not really needed to use the Ad blocking add-on. There are several Ad blocking add-ons for Safari as well as other browsers. Try searching MacUpdate.com as well as Google.
With respect to editing /etc/hosts. If you are careful, and as you said you did this before, they you can most likely do it again. However, I would point out that it is a pain to keep updating the /etc/hosts file as you find yet another offending Ad or pop-up. Plus maybe someday you find you need to visit that site (OK, maybe that is stretching it), but what if you do? The static nature of /etc/hosts means you would be blocked, and most likely never think it was because of /etc/hosts. This is also why I suggest using a Flash blocking add-on, and if you find you need it an Ad blocking add-on.
As far as dangers, you could loose localhost capabilities (actually very useful), or mess up DNS lookups. So it is a very good idea to keep the original around just in case. Another danger would be editing /etc/hosts with the wrong utility, and accidentally turning it into a Rich Text format file, or (yuck) a Microsoft Word document nano (anyone could use it), vim (steep learning curve), emacs (an operating system pretending to be an editor), TextWrangler (GUI), Fraise (GUI) are all safe text editors.