Web-based HTML snippet editor

I'm looking for a web-based HTML editor. I am NOT looking for a WYSIWYG editor. The author needs to be able to edit the HTML directly, and I'm looking for features like syntax highlighting, tag auto-completion, whitespace formatting - stuff you'd expect in a typical IDE. It also needs to be able to edit HTML snippets that aren't necessarily valid HTML on their own (for example, just a table row without table tags) without puking.

Does anything like this exist?