This article was previously published under Q239495
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When you are browsing the Web through the Microsoft Proxy Server 2.0 Web Proxy service, the client may receive old data in the browser.
If a client request contains an If-Modified-Since entry in the HTTP header and the target object is cached but expired, the proxy adds a second If-Modified-Since header, which is an undefined condition in HTTP. This is a fairly common condition because of browser caching and downstream proxy caching. Depending on which If-Modified-Since entry the publishing server decides to honor, the problem could lead to old data getting returned the client.
To resolve this problem, obtain and install Microsoft Proxy Server 2.0 Service Pack 1 SP1. For more information about Microsoft Proxy Server 2.0 Service Pack 1, please see the following article in the Microsoft Knowledge Base:
238375 Proxy Server 2.0 Service Pack 1: List of Fixes
Microsoft has confirmed that this is a problem in Proxy Server version 2.0.
The problem is corrected by Microsoft Proxy Server 2.0 Service Pack 1.
For additional information, visit the Microsoft Proxy Web site: