I've been using MathML for a while now for some of my documentation work on 3D graphics. Unfortunately the only way at the moment is to use XHTML 1.1 modular doctype to include either or both of MathML and SVG. In HTML 5 these have become embedded content parts of the specification. So for example, using MathML would be as simple as doing:

```
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>MathML test</title>
</head>
<body>
<math>
<mrow>
<mi>y</mi>
<mo>=</mo>
<msup>
<mi>x</mi>
<mn>2</mn>
</msup>
</mrow>
</math>
</body>
</html>
```

Unfortunately the only browser to support either MathML or (parts of) HTML 5 at this moment is Firefox 3.5. However, the MathML or SVG embedded content did not render under 3.5. After reading John Resig's post about a new HTML parsing engine in Mozilla's Gecko engine I set out to test this engine's support by downloading the latest nightly and setting html5.enable to true in about:config and 'lo and behold, it renders as expected.