If you want to make money from web advertising, you would be expected to produce visitor figures for your site. The more traffic that is likely to see their ads, the more money you would expect from advertisers. Of the sites I maintain, 1 has 60,000 hits a month and can produce a nice revenue. Some advertisements work on a click-through basis. If someone visits the site, clicks on an advert/link then proceeds to make a purchase, I will earn a commision on that sale. This method reduces the risk for the advertiser and can be suitable for new websites, that take a while to appear in web searches, directories etc.