Ace is an open source, standalone and web-based code editor that focuses on providing a similar or better experience with desktop-based ones.
It is actually developed for the well-known Cloud9 IDE and can be integrated into any web page easily.
There is support for auto indent/outdent, completely customizable key bindings ad theming.
Users can perform search/replace operations with regular expressions besides the standard method, toggle between soft tabs + real tabs and much more.
Compatibility: All Major Browsers