If you want to put advertisements in your website so that you can earn revenue from it, then try google adsense or www.bidvertiser.com. In the first case, you first create an account in gmail and then apply for adsense by submitting your website. If google approve your site, then only you can put ads. In the second case, it is also free to put ads to your site, just try it (I myself is only using google adsense, have no idea about the second one).