McAfee’s SiteAdvisor service released a report yesterday looking at how risky web pages returned in search results from five major search sites were in May 2007 and comparing the results to May 2006.

The study found that 4% of search results from Google, Yahoo, Microsoft, AOL and Ask lead to risky web pages, an improvement of one percentage point on the year.

This improvement was led by cleaner sponsored search results from Google and Ask (which uses Google’s advertising), but dragged back by less-safe results from Microsoft and Yahoo. AOL was the safest search engine.

McAfee’s definition of risky is broad, however, and includes sites that engage in legal high-volume emailing and/or pop-up advertising – annoying, certainly, but not really a security threat.

Excluding these lower-risk categories of activity, which McAfee categorizes as yellow, the percentage of serious red sites, which try to install adware, send spam or change user preferences, was a more modest 1.87%.