With CPM (cost per thousand impressions) advertising you get paid a fee, based on thousands of impressions, when an ad is displayed on your site. This is the kind of web advertising that is the most like traditional media advertising: an advertiser pays for displaying its ad in a magazine, on television, or on a web site, end of story.
CPM ads can either be text-only or provide graphics. The bulk of banner ads that you see on the Web have been placed on a CPM basis. In fact, one of the pitfalls of accepting CPM advertising is getting stuck with garish imagery, Flash-based animations, as well as assorted pop ups and pop unders, which can irritate and distract visitors to your web site.
CPM advertising cannot be expected to generate a very high click-through rate and does not pay very much per impression. Typical CPM ad rates are in the $4 to $6 range per impression, although significantly higher fees can be achieved in special situations (for example, when a CPM sponsor underwrites an entire site).
Obviously, with these economics, making money from CPM is a volume affair. For the most part, to even participate in CPM programs you need a minimum of 500,000 monthly page views. If you do have this kind of volume, you can find a great deal of information about CPM advertising from the trade association that works with the Internet CPM industry, the Internet Advertising Bureau (http://iab.net). Depending on your organization, it's reasonable to negotiate directly with CPM advertisers or to sign up with an agency such as MaxOnline (http://www.maxonline.com).
While it remains true than you need high volume to make any real money from CPM ads, there are beginning to be some CPM options for lower-volume sites. You can join Fastclick 's CPM program (http://www.fastclick.com) with as few as 3,000 site impressions per month. AdBrite (http://www.adbrite.com) has no minimum volume requirements and lets you set your own asking price for text ads running on your site (this is not technically CPM advertising because you are not paid per impression, but it can amount to pretty much the same thing depending upon the pricing structure you set).
As you may know, Google's AdWords program now accepts site-targeted CPM advertising. This means that if your site is enrolled in Google's AdSense program, you can automatically receive some CPM revenue (provided you choose certain settings in the AdSense program). For more details, see Chapter 8.