Recently I wanted to implement a way of directly editing script files from my server on a browser window.
Looking around for prospective projects, the most prominent one looked as ACE: http://ace.ajax.org/ from the Cloud9 IDE. Looked nice and I gave it a go for a day. Unfortunately, I found myself struggling to make it work as required for my purposes and it was not working under Internet Explorer.
Interesting enough, I got it working as intended under 30 minutes and it was working fine under IE as well as other browsers. As far as I'm concerned, CodeMirror has gained me as a fan of their project.