Math equations on the web
How can I render Math equations on the web? I am already familiar with LaTeX's Math mode.
The other answers are out-of-date. As of 2012, beautiful math is easy to write and render. The technology is called MathJax. You can see it in quiet action on MathOverflow and hundreds of math blogs.
MathJax is an open source JavaScript display engine for mathematics that works in all modern browsers. No more setup for readers. No more browser plugins. No more font installations… It just works.
Mathjax is reliable and unobtrusive, so you just need to write the math. You do so in Tex (Latex), a concise syntax with which most scientists and mathematicians are familiar (and have shared decades of good tutorials). For Mathjax, you simply write Tex code in-line in your HTML between double dollar signs, eg.
When $$a \ne 0$$, there are two solutions to $$ax^2 + bx + c = 0$$ and they are $$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$
To use Mathjax to render your math, put a Javascript line in your HTML header:
<script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js"></script>
If you publish on a platform such as Wordpress, Tumblr or Blogger there are plug-ins in their galleries to do this (Wordpress).
How does Mathjax render math? With Javascript it renders your math to beautiful HTML and CSS (remarkably resembling Latex) in a fraction of a second. If a browser supports MathML, it can render math through that too, but that's not important. It's a popular success because the end-user workflow is easy, not because of the technology behind it.
You can choose to use Mathjax (over png images) on Wikipedia if you have an account. Look for Special:Preferences / Appearance.
MathML is ridiculous. It's neither human-readable nor human-writable (the quadratic equation takes 800 characters - it's 50 in Tex). It's just another pointless XML language . Thankfully, it's obsolete before most browsers support it. It doesn't even look as good as Tex or Mathjax's HTML-CSS!
It turns out this is a bit of a pain.
You can use MathML, but browser support is still iffy. If you are starting with latex you've got a few options for converting to html, but they'll all typically end up rendering the actual equations to images and inlining those.
Nothings all that pretty (unless you resort to pdf or something). What's best will depend a bit on what sort of content, how many equations, and how complicated the equations are.
Here is a decent summary.
My two favorite approaches:
Client-side: MathJax. See some examples here. It is very easy to use and install and its development is backed by the AMS and SIAM among other scientific institutions. I expect this to become the defacto standard for displaying math on the Web.
Server-side: LaTeXML. This is used for producing the NIST Digital Library of Mathematical Functions. It tends to hiccup if you have custom macros in your TeX sources but in general it does give very good results.
The jsMath package is another option that uses LaTeX markup and native fonts. Quoting from their webpage http://www.math.union.edu/~dpvc/jsMath/:
The jsMath package provides a method of including mathematics in HTML pages that works across multiple browsers under Windows, Macintosh OS X, Linux and other flavors of unix. It overcomes a number of the shortcomings of the traditional method of using images to represent mathematics: jsMath uses native fonts, so they resize when you change the size of the text in your browser, they print at the full resolution of your printer, and you don't have to wait for dozens of images to be downloaded in order to see the mathematics in a web page. There are also advantages for web-page authors, as there is no need to preprocess your web pages to generate any images, and the mathematics is entered in TeX form, so it is easy to create and maintain your web pages.
See for example this page or that one.