I had to laugh when I read "Indoorsman"'s response to this sentence. You know you're a slave to web design when a friend calls and says "dude, are you alive?" I get phone calls from friends and family all the time too, and most of the time they do understand the fact that I'm working, but they do wonder what is so fascinating about those < and > characters!
Some other hilarious responses I've gotten include:
"the only computer gaming you do anymore is playing with CSS on random sites in Firebug"
"you visualize in your mind how TV commercials could be done on a web page"
"you find yourself meeting new people and the first five minutes of conversation you are asking if they have a web presence"
"when you're shopping for a car and tell the dealer that you want something in a shade of #929175."
While I can't say that I've asked for a car in a hex color shade, I have found myself testing myself to see if I can guess the hex code for random colors. And I do admit to thinking about how to code a TV commercial on the web. Once I even found myself pausing an episode of Burn Notice so that I could sketch the opening titles to see if I could mimic them in a web design (the scene where Michael is standing at the top of stairs looking around a building with Sam behind him, if you watch the show).
Finish the sentence You know you're a slave to web design when...