McAfee, of course, is known for antivirus and (belatedly*) antispyware. When you install SiteAdvisor on your web browser, a small button displays in your web browser toolbar. At the simplest level, green means good, red means bad, and yellow indicates caution (gray indicates no data). You can click on the button (or put your mouse over it) to find details about the page.
Even better is the way it handles Google searches. When you search on Google, SiteAdvisor displays a check mark or and "X" to indicate if the page is safe. Click on the icon will give you the details and reason for that analysis.SiteAdvisor is available at http://www.siteadvisor.com/. It works with both Internet Explorer and Firefox (and will detect which one you are using).
*Most antivirus vendors took much too long to get involved in antispyware.