This package is called mathJax. You can read about it from its home
page at http://www.mathjax.org/
.
The page so made can be read with any current browser (I am told) and looks quite reasonable. It does not require tex/latex fonts to be installed on the reader's computer.
Of course many of us have been posting (La)TeX math by making a pdf file and posting that. The advantage of mathJax is that you can use the features available in HTML, in particular links and easy editability.
If you want to try making a page that uses this,
copy the first <script>...</script>... into the head section
of a file, and insert latex equations, but not $\theta$ (use \
If you really want to use single dollar signs for equations, add
<script type="text/x-mathjax-config">
MathJax.Hub.Config({
tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']]}
});
</script>