Snorkeling with shares of Pandora, LinkedIn and Demand Media

If you didn't, you've been underwater since.

But I don't mean just underwater: I mean so far down that you can see shipwrecks and lost civilizations. Demand's stock closed Wednesday at 6.21. That's a loss of 75%, and that's what you get when you seek IPO investing advice from eHow.com, Demand's flagship junk content repository.

Keep all of this in mind when the underwriters for Groupon and Zynga try to play you with their last-minute offer-price increases and tales of road-show exuberance. It's all a con.

Again, I'm not saying it's a bad idea to buy shares of a new Internet offering. I'm saying it's a bad idea to buy on the first day, when emotion trumps reason. You'll have plenty of chances from the second day on.