Some commercial sites market on the basis of guaranteed impressions, eg the minimum times a banner will be seen as the user navigates through the site. A page often contains text plus images, ie comprises several data files, each of which constitute a 'hit' when retrieved by a browser Page views or page deliveries - the number of times a web page is requested. Page views, not hits, are the preferred counting method for site-traffic estimates and measurement. Unlike a hit, a request doesn't include client or server 'errors' Response rate - the percentage of impressions that result in clicks. Also called the click rate.
Sites often use identifiers such as cookies to differentiate between users.