[TheGorramBatman]

MathJax integrated asciimath long time ago: http://docs.mathjax.org/en/latest/asciimath.html

[Animats]

The site has no date information, but says "currently this only works in Firefox 3+ and Safari 5.1+", so this goes back many years.

[amathprof]

The original native AsciiMath script was limited in support, but AsciiMath via MathJax has wide browser support. We maintain the original script still, but most people use AsciiMath through MathJax.