Single sign in facebook URL Error

I successfully added the single sign in frm facebook in my application.

But there is an issue now.

In facebook when I created the application I added the url as:

http://websitename.com/MemberAccess.aspx

Because

when I access typing  http://www.websitename.com/MemberAccess.aspx

it gives invalid url error

how to solve this issue to use both with www and without www in url