E-advertising is often measured as a Cost Per Impression (CPI) or Cost Per Thousand Impressions (CPM). This is not a new technique, traditional marketers have been using something similar for ages. Whether you advertise on television, radio, magazines, newspapers or billboards you will often look to CPI as your justification for the cost.
For example if you know that your advertisement will be seen by one million people and you are quoted a CPM of $ 10.00 your total advertising cost will be $ 10,000. The CPI then divides this number by 1,000 so that a $10.00 CPM equates to a $ .01 CPI.