TinyMCE is a platform independent web based Javascript HTML WYSIWYG editor control released as Open Source under LGPL licence by Moxiecode Systems AB. It has the ability to convert HTML TEXTAREA fields to editor instances. It's easy to integrate with your existing system and very useful! For me it is super, but I need to insert into HTML custom tags (like code and acronym as well. So searching for informations "How to do it" on internet was for nothing. I made special plugin for insert into editor code and acronym element. It is working on Gecko and IE as well.
Download TinyMCE plugin CELEMS.