IE lets you set custom security settings for different zones: Internet, Local Intranet, Trusted Sites, and Restricted Sites. When you visit a website, IE automatically classifies it as in the Internet zone. The exceptions are websites hosted by your local network (say, a site set up for use on your company's network)--then it's Local Intranet--or sites that you've added to the Trusted or Restricted lists beforehand. You can set each zone to a predefined security level and customize the settings as well.