MathJax Test Page
If you see typeset mathematics below, then MathJax is working. If you see TeX code instead, MathJax is not working for you.
\[ \frac{-b\pm\sqrt{b^2-4ac}}{2a} \]
MathJax is not working!
Once you have MathJax working properly, view the image mode test page to make sure that the image fallback mode is working as well.