This sounds like a good idea and if implemented well, I think it will improve web security for a lot of users.
Basically, Site Advisor gives you the results of automated searches which rate the conduct of the web site you want to view. Should it deliver adware, spyware or (Heaven forbid)something worse, the application will alert you. There will be two versions of the software; one paid for and one free. I'm not quite clear on the differences so I can't comment on that.
Done well, this could mean a virtual end to "drive-by downloads" and spyware bundled with desireable applications. All the user has to do is pay attention, though I must admit I know more than a few who will not do so, no matter what. Versions are available for Internet Explorer and Mozilla Firefox and function as browser extensions.
I intend to install and test this and if any or our listeners want to do so, we can pool our experiences for a report on the show in a week or three.