CPM advertising systems behave virtually as PPC systems, except that you will get compensated based on the quantity of impressions (i.e., page sights) the advertisements shown on your website will generate. CPM means Cost per Mille, also it refers back to the cost for 1,000 impressions.
Your blog that creates 100,000 page sights monthly exhibiting a marketing banner having a $1 CPM, therefore, will earn $100 monthly.
CPM rates vary using the network, the positioning of the ad and also the format. The greater the network, the greater the CPM rate (simply because they get access to more marketers). The closer you place the ad to the top page, the greater the CPM. The higher the format (when it comes to pixels), the greater the CPM.
You will get as little as $,10 and up to $10 per 1,000 impressions (more in certain special cases). CPM advertising tends to be effective online having a high page sights per customer ratio (e.g., online forums, magazines and so forth).
Listing of popular CPM advertising systems: