Background:In May 2008, California became the second state in the U.S. (after Massachusetts) to allow same-sex marriage. Anti-gay activists put a measure on the California ballot to change the constitution to make marriage only between a man and a woman. Prop 8 passed 52-48%. Gay and lesbian couples are no longer be allowed to marry in California.
Update:On June 26, 2013, the United States Supreme Court ruled that Prop 8 is unconstitutional. Same sex marriage is now legal in California.
Sources: No on 8, HRC, Los Angeles Times