I wasn't aware that there is a dress code for concerts. Of course, I'm not one that wears clothes to be cool or neat, either.
I wear whatever's comfortable. I've been to a few concerts, and wore a regular t-shirt and shorts everytime. I've heard that you're "not supposed to wear the band's shirt" before, but I'm still baffled that people have a dress code for going to concerts. Maybe I'm just not in-the-cool.
-Lasereth