Request.ServerVariables("HTTP_REFERER") - What is going on?

NIS by default blocks the header "HTTP_REFERER" to be sent from the browser to the server. If your web application is depending on this servervariable, and your clients are using NIS, then do the following:

NIS:
- Privacy control - configure
- Advanced button
- Global settings tab
- "Information about visited sites"

If blocked (this appears to be the default) then HTTP-REFERER is wiped out. Change this option to allow the header to be sent.