Mozilla keeps stalling and crashing whenever I try to view videos online, or check my email.

Question

Whenever I try to check my email, or watch videos [on YouTube], Mozilla Firefox stalls--seemingly frozen--then I end up having to force it to shut down. And when I try to open a new window and restore the session, the screen appears frozen and unresponsive.
Before posting this question, I made sure that all of my plug-ins were updated, my computer(Windows-PC) is virus-free, and that I was running the most recent version of the browser. However, I'm using Google Chrome to post this question. I have uninstalled Firefox out of frustration.

Answer 1

Create a new profile as a test to check if your current profile is causing the problems.
See "Basic Troubleshooting: Make a new profile":
* https://support.mozilla.com/kb/Basic+Troubleshooting#w_8-make-a-new-profile
There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.
If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.
See:
* http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox
See:
* http://kb.mozillazine.org/Firefox_crashes
* https://support.mozilla.com/kb/Firefox+crashes
* https://support.mozilla.com/en-US/kb/latest-firefox-issues
If you have submitted Breakpad crash reports then post the IDs of one or more Breakpad crash reports (bp-xxxxxxxx-xxxxxxxxx-xxxx-xxxxxxxxxxxx). You can find the IDs of the submitted crash reports on the about:crashes page. You can open the about:crashes page via the location bar, like you open a website.
See:
* http://kb.mozillazine.org/Breakpad (Mozilla Crash Reporter)
* https://support.mozilla.com/kb/Mozilla+Crash+Reporter
* https://developer.mozilla.org/en/How_to_get_a_stacktrace_for_a_bug_report