It's a photo of a banner that he, Steve Jobs and Allan Baum were going to unfurl off a roof during graduation or something. If you look closely, you can see the word SwabJob on the bottom, which was mashed up out of the initials SW, AB and "Jobs". They got caught before the prank went down, and I think, later it was revealed that Jobs was bragging about the prank to someone, which lead to them getting caught.
Anyhow, the site is fun. If you've got geeky childhood photos of you, please send em over to [dorkyearbook.com.]