The symbols are misaligned. What happened?
The MathJax font package was changed for the v1.0 release. You might be using an old version. To fix this, you must completely remove your fonts directory and replace it with the 1.0 fonts. Both the actual font files and the font metric information in the MathJax code changed in beta 2. If you only update one or the other, they will be out of sync, and characters will appear badly misaligned. Remember to unzip MathJax-webfonts.zip! Merely replacing the zip file will not update your installation unless you unzip it. This also applies to svn users, who will need to delete the mathjax/fonts directory and unpack the new fonts.zip file. If you get the latest version via svn, the fonts.zip file will take some time to downlaod, as it is approximately 13MB in size, so be patient. Also, be aware that some browsers cache web fonts, and depending on the browser, there may not be an easy way of clearing the cache. Exiting and restarting the browser seems to work fairly dependably though.