Custom WYSIWYG Editor

I need a very simple WYSIWYG Editor, to replace a HTML text area, The twist being I want to define a few custom style tags eg: ## Deliverables Deliver a WYSIWYG editor, that reflects changes, and when saved sends the text, including costom tags. (the custom tags get processed by a php script later down the line) so 1 WYSIWYG Editor using custom Tags An ability to easily add more custom tags ## Platform Javascript, can use php ajax, and lysql if required IE5+ and Firefox