I guess it's not a big deal. I usually don't think 11 years makes a difference but usually it's when the girl is a bit older. Some people my think it's a big deal because you are still technically in your teens.
Side note though: age can play some of a role in a relationship, such as relating to certain topics, the fact that your date probably remembers the 80's and you were only around for the latter half could be interesting.
Anyway there are no hard rules here. Good luck.