Graffiti is an art form usually frowned upon, but for one day out of the year during the Ann Arbor Art Fair, it’s actually encouraged.  The Ann Arbor District Library hosts its 8th annual Teen Graffiti Art Contest in the Downtown Library’s staff parking lot on Friday, July 23 from 11 a.m. to 1 p.m.  Teens in grades 6-12 are invited to use spray paint to create graffiti on canvas to be judged by peers and adults.  First, second, and third place winners will receive gift cards for art supplies. Many of the graffiti pieces will be selected for a special exhibit in the Downtown Library.  Supplies for the contest will be provided by the library. 343 S. Fifth Ave, Ann Arbor.  For more information, call 734-327-8301.