What you need to know about security zones

Internet Explorer divides your Internet world into zones, so that you can assign a Web site to a zone with a suitable security level.

You can tell which zone the current Web page is in by looking at the right side of the Internet Explorer status bar. Whenever you attempt to open or download content from the Web, Internet Explorer checks the security settings for that Web site's zone.

There are four different zones:

Internet zone: By default, this zone contains anything that is not on your computer or an intranet, or assigned to any other zone. The default security level for the Internet zone is Medium.
Local intranet zone: This zone typically contains any addresses that don't require a proxy server, as defined by the system administrator. These include sites specified on the Connections tab, network paths (such as \\server\share), and local intranet sites (typically addresses that don't contain periods, such as http://internal). You can also add sites to this zone. The default security level for the Local intranet zone is Medium.
Trusted sites zone: This zone contains sites you trust - sites that you believe you can download or run files from without worrying about damage to your computer or data. You can assign sites to this zone. The default security level for the Trusted sites zone is Low.
Restricted sites zone: This zone contains sites you don't trust - that is, sites that you're not sure whether you can download or run files from without damage to your computer or data. You can assign sites to this zone. The default security level for the Restricted sites zone is High.

In addition, any files already on your local computer are assumed to be very safe, so minimal security settings are assigned to them. You cannot assign a folder or drive on your computer to a security zone.

If you want, you can change the security level for a zone; for example, you might want to change the security setting for your Local intranet zone to Low. Or, you can customize the settings within a zone from the default settings in Low, Medium Low, Medium, and High.