[xymostech]

We reimplemented the TeX formatting algorithms in JavaScript. Most of them are in https://github.com/Khan/KaTeX/blob/master/src/buildTree.js (there are references to the pages from the TeXbook that the algorithms are on).

Also, we attempt to have relatively good error handling! If you open up the javascript console on the main page and type in a bad expression, you can see what the errors we throw look like. We're not planning on supporting anything other than LaTeX syntax for now though, unfortunately.