Have a look at your competition such as; http://supergenpass.com/

Your system is creating the passwords server side and so taking the user's "master" password in. Where as SuperGenPass is purely javascript based and runs completely in the browser; thus is safer.

Also being a bookmarklet make's it more convient, as you can just click the button from within your browser toolbar, rather than having to go to a sepearte site, remember exactly what you put in the "Create password for:" input, did you put the domain with a www or without? with http:// or https:// ?