Also reported at http://support.microsoft.com/support/feedback/ Posted here FYI (because it wasted an hour or so of my time)
When executing : Response.Redirect("~/default.aspx?user=" & userID) when userID is a Windows Authenticated user (ie is in the form "domain\user"), the "\" is changed to "/" (A bit of a PITA when you then look this up in a database for user-specific data) It looks like despite \ being valid in the QueryString, Response.Redirect simply replaces \ with / (probably to fix URLs) regardless of it's location Server.HTMLEncode does not affect this character, so you have to mung it manually :-( Merak You can read messages from the DOTNET archive, unsubscribe from DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.