Ways To Monetize Your Blog - Display Advertising
Display Advertising is different from Contextual Advertising because instead of paying you by CTR, Display Advertising pays you by CPM. CPM means Cost Per Impression.
Every time a reader sees your display ad, you will make a small amount of profit. With CPM ads, you would make more form impressions than if you had contextual ads. CPM ads are good for forums (where you can get thousands of impressions a minute) or pages where you don't want your visitor to leave through a contextual link.
CPM ads are not really recommended for blogs, as most bloggers make more through contextual advertisements.
Google Adsense official page has this to say about CPM ads:
CPM stands for "cost per 1000 impressions." Advertisers running CPM ads set their desired price per 1000 ads served, select the specific sites on which to show their ads, and pay each time their ad appears.
For publishers, this means revenue in your account each time a CPM ad is served to your page. CPM ads compete against pay-per-click (or CPC, cost per click) ads in our ad auction, so only the highest performing ads will be served to your pages. Advertisers will need to bid a higher CPM than the existing CPC ads in order to show.
CPM ads can be either text or image ads, and are always site-targeted. CPM text ads will expand to take up the entire ad unit.
