Urban Markup Language
You've seen those spray-painted marks on the street - usually they have a line, arrow and read USA". As a planner, you have this nagging sense that you should know what they are.
A one-page feature in the September issue of Wired Magazine offers nine images of the most common forms of the graffiti, along with descriptions of what they mean. (Unfortunatley, the web version doesnt include the great photos.)
For example, USA stands for underground service alert", a blue line is for water, and a red line for power.
Thanks to Chris Steins