I recently started using Firefox 4. It seems that the browser understands MathML. However, the output is not as pleasing as the old MathJaX. Will this improve when Firefox 4 gets out of the Beta phase? Is there a way to get the old MathJaX back? I guess this question will become relevant in the near future when "everybody" will change to Firefox 4.
Now that Firefox 4 has been released, this is a real problem. The HTML/CSS rendering of MathJax here does not use the MathJax TeX fonts, but instead seems to use the default serif font of the browser, making the rendering look terrible. The problem does not occur in the demos on the MathJax site, which suggests that this is a problem with the deployment of MathJax here on StackExchange.
Here are some screenshots taken on Linux of an post by Michael Lugo which conveniently had a lot of formulae in one place.
Firefox 3.6.15, HTML/CSS (this is the right behaviour):
Firefox 4.0, HTML/CSS:
Firefox 4.0, MathML:
The Firefox 3 HTML/CSS rendering is clearly the best of the three, as all the symbols are of the right size, and the math font's height and width is almost identical to that of the body text. On Firefox 4, the HTML/CSS rendering is clearly broken while the MathML rendering, while readable, is too small and uses too narrow a font compared to the body text.
Dear StackExchange admins, this is a bug; please fix it.
This should be fixed now that MathJax 1.1 is deployed.
We will be sponsoring the MathJax project as well, with more details to be announced later.
Using firebug, I can see that the HTML is not the same from 3.6.16 to 4.0. However using User Agent Switcher to make 4.0 look like 3.6.16 does not seem to help.
Boris Zbarsky was nice enough to really dig into this and add a lot of detail to the bug (http://bugzilla.mozilla.org/show_bug.cgi?id=644885). Apparently, it has to do with how MathJax determines whether downloadable fonts are supported. MathJax 1.1 does this correctly for FF 4.0.