I was taking the go tour [0] and got curious about their clean code editing interface. Looking at the source code it seems that they use codemirror.

0: http://tour.golang.org/

For some reason, they didn't write a language mode. Something that just recognizes comments, strings, and keywords would be extremely trivial to do (for example http://codemirror.net/mode/vbscript/vbscript.js )