It is normal for there to be lots of warnings and errors in the error console. They are mainly of use to web developers.

I also have a lot of errors for yahoo, yahoo does not run right, sound on videos are slower than the picture and some times it sounds as if the video is studdering and also it says chrome cannot be read, I dont even have chrome running

Tom

As posted above, you can ignore (CSS) errors in the Tools > Error Console.
Those errors are only useful if you develop websites and want to check the HTML/CSS and JavaScript code for errors.
Most errors are code for other browsers like IE or browsers on other platforms or just typos or the result of bad coding.

This may be caused by a recent Flash 11.3 update.

See:

• https://support.mozilla.org/kb/keep-flash-up-to-date-and-troubleshoot-problems
• https://support.mozilla.org/kb/flash-crashes-or-does-not-load-firefox-13

• http://forums.adobe.com/thread/1018071?tstart=0
• http://blogs.adobe.com/asset/2012/06/inside-flash-player-protected-mode-for-firefox.html