I couldn’t see anything in the settings, so I went to the help pages.
Couldn’t find anything in the help about turning something like that on either.
But I did find a discussion about it:
Firefox doesn’t need a “compatibility mode” like IE has - Firefox has always been more compatible with W3C standards than earlier versions of IE were and doesn’t need that “mode” like IE does to display web pages made for older versions of IE without breaking those web pages.>
Unfortunately that’s just not true. Here is an example of a site that’s not viewing correctly in 4.0. That compatibility mode is still needed. ___________________>
This page looks fine to me in Firefox 4.0. ___________________> Try clearing your browser cache. Tools > Clear Recent History… - hit Details and make sure only Cache is selected, then select Everything and hit the Clear Now button.
I tried the page that the poster said had been broken and it seems to display fine for me, too.
So, it seems as if some people have problems getting pages to work, and others have no issues.
If I knew what was different in my settings (other than the clean install on the PC and the clean install of Firefox), I’d share.
It may be (as quick guess) that it is some plugin for FireFox, and not FireFox itself, that causes some pages to be broken for some users. That would at least explain the noted behaviour, but I don’t know which plugin(s) to suggest disabling.
Well, either that, or I got the magic special copy of FF4, just like I keep getting the magic special WDTV firmwares, where things work for me that don’t work for anybody else.