MathML was supposed to be the answer, and we all know how that went. Just goes to show how over the top people were going with XML in the late 1990s. I mean,
MathML is not a human input language! MathML is a representation. While comparisons with TeX and LaTeX are inevitable, they serve different purposes. Look at the HTML/CSS used to render a dynamic menu sometime. I'm sure it is pretty ugly too.
It always surprises me how difficult math on the Internet has turned out to be. Hopefully this can help...