Internet Explorer's zone model
The zone model in Internet Explorer assigns each Web server visited to a specific zone. The browser observes discrete security settings for the respective zones, which makes it possible to enable functions for trusted servers, such as local intranets, which should not be permitted in general. Internet Explorer distinguishes between four zones.
The Internet zone
This zone includes all Web sites that have not been assigned to one of the other zones. All Internet sites visited for the first time that have not been listed in another zone are automatically placed in the Internet zone; thus, this zone is the most important.
The local intranet zone
This zone contains all of an organisation's internal addresses, which are, for instance, allowed access to databases or shared calendars. Users can work with all features provided by MSIE without risking external attacks.
The trusted sites zone
This zone may be used to access servers whose content can only be displayed correctly with low security settings. Users should be sure that the respective site operators are truly trustworthy. This includes measures to protect the servers against attacks since you as a visitor are also exposed to related risks indirectly.
The restricted sites zone
Restricted sites are the counterpart to trusted sites. In this zone, users should enter addresses of sites that are deemed potentially damaging, such as sites with objectionable content, which may work with a (costly) dialer. By default, the Outlook Express mail client receives the security settings for viewing HTML mails from the restricted sites zone.
The Internet Explorer's preconfigured standard levels provide a reasonable compromise between security and usability. Users may also define more than 30 individual settings themselves. Here you learn how to do that.