BPA Worldwide reports that average web site traffic for July dropped somewhat compared to the month earlier for the business-to-business and consumer sites it audits under the BPA Interactive service.

Perhaps not surprisingly for a summer month, average unique browsers per site dropped 17%, while user sessions decreased 1.1%. Interestingly, while fewer people were visiting, those that did viewed more pages as page impressions rose 9.9%.

The average traffic is derived from 522 separate sites audited by BPA around the world, though most titles are based in the U.S. BPA says the number of sites participating in its Interactive web traffic tool climbed 15% from a year ago. Of the 522 sites, 254 are reporting “live” data that is available free of charge to registered advertisers and media buyers, while 268 “non-live” sites are in various stages of preparing to release their data to the marketplace.

BPA summarizes site traffic across different industry categories for business publications, and also different consumer categories. Below is the summary for July 2010 (not including the newspapers BPA audits). BPA Worldwide operates under its CCAB division in Canada.