From Finjan Software:
You're careful. You limit Facebook interactions to trusted friends. You only click on search engine links that look valid. Safe, right? Well, not exactly. Because most malware infections are now spread on legitimate sites, it's hard to know whether clicking that trusted link will lead to an attack that could compromise your identity or privacy.
SecureBrowsing changes that. This free security plug-in gives you an easy way to tell whether a Web page is infected before you click.