Where can I find a return url on my site?

Your return URL is usually the homepage of the site you are creating. It also might be asking you for "where do you want people to go to when they click your banner." For instance, if I clicked on your banner it would take me to yahoo or something. But return URL is usually the URL of your homepage.

He is asking for the url where you will place his banner or link.

He might be interested in 3 way link exchange (ie he will place you link or banner on his website and in return you will place his banner or link on your website other than your website which he has place on his site).

If you both are doing reciprocal exchange that just give him your website url on which you will place his banner or link.

It depends on the policy of the exchange program. Basically, it requires you to locate their banner on where visitors can read or see it. Don't put them in "invisible place". Main page or the page of your link which you have used in this exchange program.

cam4 is telling me to validate my email how do I do that