Make money with Google - Adsense

AdSense program lets you sell advertising space for other people's ads on your website, ads that are relevant to your site's content pages. You earn money everytime someone clicks on the advertisment.
It's one of the fastest and easiest way to generate revenue from a website that contains great content.

Yep, your website content is pretty important. But it's more important to make money and this is pretty decent way to do it.