I put an ad on the yahoo personals but i can't view mine nor others profile. Why? this is a free service?

If you just set it up, your profile has to be reviewed first. They tell you that when you send it off after creating it. That could take a few days. I believe you can look at profiles even if you're not a member. Yes, it's a free service, unless you want to contact someone, then you have to pay a monthly fee. I don't know if you're doing something wrong not to be able to view other profiles, or if you got a message from Yahoo that you can't. You didn't say how you came to that conclusion.