Selling advertising is a classic way to profit a web site, and it's still playing very important role when web site owners want to make money from their web sites.
Right now, most of people work with Google Adsense, or Yahoo Publisher Network to get the advertisement. But there is still another great way which will only use very limited place of you web site, and is still able to bring you considerable earning. It is to sell the link in your web site.
