@ETpro is also correct.
If you’re talking about ads that businesses purchase on your site, then yes you’ll make money from them, but no one will buy them unless you have high traffic.
If you use Google AdSense, you’ll make a small amount, larger if you bring in tons of visits.
Same with affiliate marketing (see www.cj.com if you want to try that out).
Newspaper websites, which depend heavily on ads, charge advertisers by CPM – cost per thousand impressions. So even if people see their ad, they get money. That’s the upper end of ad-based monetization of a website.
If you’re looking to make some money online, here’s a few of the best suggestions I can give you (other than diving into eCommerce yahoo stores with our friend @ETpro there)
All these suggestions can be done with a small website, a little seed money and a lot of innovation and creativity, but it’s the basics of making money on the web (aside from advertising and such):
1) Do you have any skills or specialties? Sell your services on the website
2) Create eBooks, White Papers, high-end content that you can sell per download
3) Create a forum or directory in a small, high-end niche and offer to list businesses in it for a fee.
4) Pick a broad niche or topic you like (TV perhaps?) Create awesome content, and then sell back-links (I call them “text ads”). If you’ve got a great site with great content, with a broad niche, people will be throwing money at you for links to their site. However, google does not like paid links, so it is a risk, you just have to learn how to fly under the radar.
There’s also a few websites you can use to make a few bucks, like fiverr.com and etsy.com (if you’re the crafty type).
Lastly, depending on your server, you could always sell hosting.
Good luck!