This mathml.css stylesheet is a simplified version of the MathML for CSS Profile without CSS table rules that had only been implemented in Presto and using new CSS3 selectors and flexboxes. We know from Opera's experience that relying exclusively on a fixed set of CSS rules to do math layout is not reasonable. This stylesheet is only intended to provide some fallback to browsers without MathML support in order to make basic mathematical constructions readable, without claim of rendering quality. For heavier polyfill with better MathML support see mathjax.js. You might also consider the mathml-warning script, which displays a warning message and let the user choose one of the MathML polyfill.
This stylesheet must not be loaded in browsers that have MathML support or
it will mess up the native rendering. You must instead load the mathml.css
file conditionally via Javascript using some
browser sniffing or feature detection
The easiest way is to insert the
mspace.js
script in your document header:
<html>
<head>
...
<script src="https://fred-wang.github.io/mathml.css/mspace.js"></script>
...
</head>
...
</html>
You can see a demo page that gives an overview of the basic constructions supported and show the limitations in more complex cases.