You can simplify expression and use regular HTML markup. However, the real standard is
MathML, see
http://en.wikipedia.org/wiki/MathML[
^].
More about MathML:
http://www.w3.org/Math/[
^],
http://www.w3.org/Math/mathml-faq.html[
^].
HTML5 (
http://en.wikipedia.org/wiki/Html5[
^]) is supposed to embed it as inline element, but most Web browsers do not support it well enough, notably Trident is well behind (layout engine used in IE), see
http://en.wikipedia.org/wiki/Comparison_of_layout_engines_%28HTML5%29[
^],
http://www.w3.org/TR/MathML/chapter2.html[
^].
For different ways of using MathML and support of them in different engines, see:
http://en.wikipedia.org/wiki/Comparison_of_layout_engines_%28HTML5%29[
^].
This is a browser test:
https://eyeasme.com/Joe/MathML/MathML_browser_test_next[
^].
There are different alternative ways, such as having some engine which converts mathematical expression into bitmaps on the fly, or such bitmaps are pre-rendered off-line. If you want to provide online editor, the second way is not good enough for you. It would be even interesting if it wasn't so disgusting even to discuss. Reasonable Web standards cannot make a way into practice for years and years. First MathML standard was released in 1998, and what do we have now? And I'm not sure MathML is really comprehensive…
—SA