the rich text editors (word editors) r developed by these Yahoo or Hotmail only for IE and they have not ported it to FF or Opera (as of now!!).So it's not available there....
those r ActiveX components and FireFox for security reasons does not support ActiveX.
For MSN blogs (and possibly Hotmail) there's one tool bar available called FEdit! for FireFox to provide the functions of Rich Text Editer.
*siteexperts.com/blogging/fedit.htm
There's one extension called Composite for Mozilla to give it Rich Text Editor, and this may work for FireFox....
*composite.mozdev.org/
try usin an extension called WebmailCompose for FireFox...
*jedbrown.net/mozilla/extensions/
there's not any concrete solution yet...guys at yahoo, hotmail and other providers should realise the grownin popularity of these browsers and offer complete to these browsers....