If you have lost your math rendering you can learn a little about these things by reading the replacemath.js docs and the mathtex docs.
For now, I am using the following bit of script to render the math:
replaceMath( document.body );
Place this somewhere on your page, and it will invoke the replaceMath function that is defined in 'replacemath.js' - see the documentation about this at the link mentioned above.
Although the rendering isn't doing quite as nice a job as the watchmath version did, it's not too bad. I'll look for something better when I have the time...
PS: This blog post provides a good overview of the LaTeX rendering options that are out there.