Internet Explorer 6.0 document.domain Property Does Not Function as You Expect

When you try to set the domain property for two Web pages to the same suffix to allow viewers to see each page in a separate frame on your Web page, the two Web pages do not communicate as you expect, or you may receive Access Denied script errors when you use cross-frame scripting.

For security reasons, Internet Explorer 6 Service Pack 1 enforces security checks about the document.domain property.

To use cross frame scripting with Internet Explorer 6 Service Pack 1, you must apply the following rules :

• Set document.domain on all the pages that must communicate with other pages that also set the document.domain property.
• Do not use the domain name that you perceive on the client side to set the document.domain property. If a site must use the document.domain property, set that property to a fixed known-good value, for example, document.domain = mysite.com. In other words, do not set the document.domain property based on the value at the client, which may be mysite.untrusted.com.
• When you set the document.domain property, the new domain must be different from the current domain. Otherwise, the change does not have the correct effect.

This behavior is by design.