I wrote my own lightweight markup language, similar to Markdown, that compiles to both HTML5 and LaTeX, supports LaTeX equations (through svgtex, i.e. serverside MathJax), references, captioned figures with semantically correct <figure> tag in html, syntax highlighted code blocks, and so on.
http://www.dllu.net/programming/dllup/
See the text file written in dllup markup language:
http://www.dllu.net/programming/dllup/index.dllu
and the PDF and LaTeX versions:
http://www.dllu.net/programming/dllup/index.pdf
http://www.dllu.net/programming/dllup/index_dllu.tex
The code is very hacky (I wrote it for my own use after all) and might crash if the syntax is not exactly right.
I also have experimental vim syntax highlighting support: http://i.imgur.com/imx6XCY.png
The HTML output of dllup is valid HTML5 (http://validator.w3.org/check?uri=www.dllu.net/programming/dllup/&charset=(detect+automatically)&doctype=Inline&group=0) and should be sufficiently semantic to be usable in lynx: http://i.imgur.com/ugSXX90.png