Login to Facebook using your username instead of email
Most of you normally login to your Facebook account by typing your email id that was used while registration.
Everyone like to use a username instead of their email addresses.
Sometime in June 2009, Facebook introduced Vanity URLs to all users.
Vanity URL is one of the nice to have feature for every user. Vanity URL allows you to set a nice username (facebook.com/iamunique) in the URL instead of having a alphanumeric characters (facebook.com/?profile=abc123).
You can create your own username using this link – www.facebook.com/username
Take time and create a suitable username for your account. This is a one-off task and it can’t be changed forever.
Once you create the Facebook username, you can use the username to login to facebook instead of your email id.
However you are still will be able to login to Facebook using your email address.
Vijay For Victory

Thanks Vijay for the tip.
Actually I have created a user name sometime back..but I don’t know we can use this name as user name instead of mail address.