The Hard Rock Cafe is helping you to celebrate its 40th birthday with a $4 burger–a great price at a place like Hard Rock.

All you need to do is register for your $4 burger here, and you’ll get a coupon that you can use at any Hard Rock Cafe location, except Tampa. No worries on that front, since this is a Philly-area blog, and we’ve got a Hard Rock Cafe at 12th and Market in Center City and a Hard Rock in Atlantic City, if you happen to be heading out to the Jersey Shore!

Note: The Hard Rock is giving out only 400,000 of these coupons. From what I can tell, there are coupons still available but you never know. Also, sign up soon because the coupon expires on December 21st, 2011.

Thanks to Houston on the Cheap for a heads up on this deal!