What version of Dreamweaver are you using?
Do you have the latest version of Design Extender, 1.1.7 installed?
What is your OS?
have you tried:
reset the workspace layout:
go to Window -> Work Space layout -> Reset '<your layout name>'
and Delete the Dreamweaver Cache file from the users configuration folder:
"Is there any extension that i can use for a membership subscription?"
data Bridge includes security assist for creating member registration and login.