Answer by Jacob Nelson:
Aptana Studio 3 should be good enough for you.
This supports html5/css3 with normal and html5 boilerplate template and have good autocompletion features.
Another editor you can try is NetBeans
Both these editors have multi language support.
ie; these editors support other languages like Java, PHP, PERL etc.The best part is, These Editors are free.
My choice is Codelobster – http://www.codelobster.com