Besides being ugly, what do PlentyOfFish, Ebay, Craigslist and MySpace have in common? They are sites which are built entirely around user-created content - the more of it, the better.

Ugly works well for these sites because it's inviting. There is no shame in posting blurry pictures, poorly spelled prose, or badly edited movies on an ugly site. After all, ugly is the norm there.

It's kind of embarrassing to see your own clunky prose and ugly photos stuck in the middle of a beautifully designed page. Unless, of course, you are a troll or a vandal, but what site wants to attract those?

Would you feel comfortable holding a yard sale in an upscale mall, a few steps from the Apple Store? Probably not. The junk from your basement would look pretty shabby by comparison. The clientele is all wrong. People might laugh at you. You would feel better - and maybe have better sales - if you set up shop at the flea market, or on a street corner. PlentyOfFish, eBay, and Craigslist are in the flea market business.

Of course, if you're trying to sell your legal services, attract paying subscribers, or encourage your users to contribute only the highest-quality content, ugly is probably the wrong design for your site.