Web Editing with Emacs tricks

this is awesome and very useful:

C-c C-f

Skip across a balanced tag group (which extends from an opening tag through its corresponding closing tag) (sgml-skip-tag-forward).   (Backward = C-c C-b)

C-c C-d

Delete the tag at or after point, and delete the matching tag too (sgml-delete-tag). If the tag at or after point is an opening tag, delete the closing tag too; if it is a closing tag, delete the opening tag too.       

C-c /

Insert a close tag for the innermost unterminated tag (sgml-close-tag). If called within a tag or a comment, close it instead of inserting a close tag.       

HTML Mode -- Emacs Manual