CPM is a fairly standard unit of measure in the online advertising business.
It stands for **Cost per thousand** (the M is the Roman numeral for 1,000). What it’s measuring is the **cost per thousand [ad impressions] [ad-impression]**.
Take [heisel.org](http://heisel.org) for example. For the month of November I had a little more than 1,000 [page views] [page-view]. If I sold ads, and if I sold them at a $5 CPM, then I’d have roughly $5 in revenue for the month.
A simple number that belies even more to talk about, but I’ve got a tree to decorate, so that’s all for tonight.