After I installed Mac OS X Mavericks on my MacBook Pro, an undesirable result was that all online math expressions generated by MathJax, such as those seen in Math StackExchange and MathOverflow, were displayed in a font that looks a lot like Times. I really hate this Times-looking font and would like the OS to return to displaying all MathJax-generated online math expressions in the standard Computer Modern font used by LaTeX. Could anyone kindly explain to me how to do this? Thank you so much!
In Mac OS, open the Font Book application (it is in the Applications folder). Drag the fonts from their archive folder onto the “All Fonts” collection at the top left of the Font Book window. If you want to install them for everyone on your computer, drag them to the “Computer” collection instead. Alternatively, you can double-click on each font and select the “Install Font” button in the font window that appears.
*If that happens to be the ugly font you're referring to, then I would presume you could uninstall it, or disable it, and MathJax will use another (default) OS X font in place of it.
There is also a fix listed here that will allow MathJax to use TeX fonts instead of STIX.