Never joke about these things.(MAN MANUAL: cosmo for your guy)

* Sure, you're a regular Chris Rock, but downing around at your girlfriend's expense is no laughing matter. Before you bust her chops, make a note of the following off-limits material.

Your Old Girlfriend

Your ex had a few redeeming qualifies, no doubt, but that doesn't mean your current flame wants to hear about them. In fact, an innocent comment about your ex's culinary skills or love of football could give your girl a serious complex.

"When you kid about something a past partner did well or go on and on about a standout attribute she had, it plants a seed in your present girlfriend's head that she doesn't measure up to this amazing Superwoman," says Robbie Reid, author of Clueless: Real Solutions for Men Who Don't Get It--and the Women Who Love Them.

Her Body

We're going to give you some credit here. Obviously you're not clueless enough to poke your babe's belly and let out a doughboy giggle. But what you might not realize is that critiquing her eating habits ("You want a little bagel with that butter?") is the equivalent of making a fat joke. "If you tease a woman about how much or what she's eating, she may view your interest as a comment on her weight," warns Robert Phillips, PhD, a ...