Hello,
I'am currently developing a WYSIWYG editor for my CMS and got serious bugs here. After switching from IFRAME to DIV contenteditable the behavior changed dramatically.
Using execCommand('formatBlock') to create headlines causes unwanted BR tags to the source code, but only in Mozilla. I thought the reason could be < br _moz_dirty=""> but I could be wrong and did not find a way to fix it.
See demo here: http://jsfiddle.net/Kj9Rp/