This repository contains some scripts to load MathJax conditionally in order to use it as a MathML polyfill. This is done by performing MathML feature detections. You just need to insert one line in your document header:
<html>
<head>
...
<script src="https://fred-wang.github.io/mathjax.js/mpadded-min.js"></script>
...
</head>
...
</html>
This will load MathJax for browsers that do not implement the <mpadded>
element (at the moment all but Gecko browsers). Replace mpadded with
mspace if you wish to verify support for the <mspace> element instead
(which is also supported in recent versions of WebKit).
Note however that MathJax is a heavy Javascript library, so in some situations you might prefer a small mathml.css stylesheet with only limited constructions for basic mathematics.
You might also consider the mathml-warning script, which displays a warning message and let the user choose one of the MathML polyfill.