Last week I had some problems to do a check wether a Rich Text Box is filled in or not. When doing a check on the Text propertie of the TextField, I found out that Sharepoint puts default something in the TextField. Like it or not, but it's really frustrating that you can't use the JQuery test .isEmpty(). So after some testing, I found out that Sharepoint puts a Paragraph tag in the TextField. So here under you can found out how I did the check wether a Rich TextField is filled in or not.