Can you recall how you originally produced the page?
Did you choose the 3rd Category on 'NEW Document' Dialog?
You don't want to try inserting a fluid div into a non fluid page.
@Binson: I'm following your post on another thread too.
Anyway, FG elements can only be inserted into FG Layout documents.
On FG Layout page if you're getting that error, you probably have some file integrity issues and DW is unable to locate your FG stylesheet.
@Ken: Thanks, Ken!
it works now.
@Sudarshan: Yes, I got it!
Thanks a lot!