She looks good, right? He's fine? You don't see anything anywhere so no way s/he's got any kind of STD... you're good. And you feel good, so you must be okay. No worries. Right? Wrong. So wrong.

Let's be clear: You cannot tell who has an STD just by looking. In fact, by age 25, half of you people reading this will have an STD, if you're having sex. (Oh, and bust out the diapers! One out of three of you young ladies will be pregnant by age 20—mostly by accident.)

What does this mean for you (yup, you again!), with your eye on that hottie by the dance floor? It means IYSL! It's up to you to protect yourself (and your partner) by always using latex condoms when you have sex. Why? Only condoms can protect you from pregnancy and STDs, if you use them correctly every time you have sex.

Feeling nervous about asking? Read our cheat sheet on how to get the conversation going. Worried about getting pregnant (or that you might already be)? You're not alone. Think you aren't at risk for STDs? Think again. Find out what to do.