Some cookies, tracking cookies in particular, send information about sites you visit and so forth back to the place that set the cookies. You should be familiar with your cookies (as funny as that sounds) and delete those you aren't sure about. The easiest thing to do is to delete all, you just have to sign in again to all the sites you visit. Don't refuse all cookies, because then you can't navigate the sites you like and remain logged in. Deleting cookies would make your computer run a little faster. Better for that is to defrag. I have my computer set to ask me if I want to accept cookies, and unless it is a site I want to login to, I refuse the cookies.
at 8:02 PM on Mar. 23, 2009