I use Microsoft ISA Server 2004, and users inside my network receive errors when accessing certain Web sites. However, they can access these sites from their home machines. How can I solve this problem?

This is a known issue with ISA Server 2004 Service Pack 2 (SP2) that relates to unsupported headers from certain Web sites. Users experiencing this problem will see a "The page cannot be displayed" message and in the "Technical Information (for support personnel)" section will see the following text: "Error Code: 500 Internal Server Error. The HTTP request includes a non-supported header. Contact your ISA Server administrator (12156)."

Microsoft has released a fix that should solve the problem for your users. You can find more information about the problem and download the fix at http://www.microsoft.com/downloads/details.aspx?FamilyID=EBC32D50-2E9F-4D55-AEFFEEBA511827B0&displaylang=en.