The VaryByCustom can be any text that represents custom output-caching requirements. If a custom string is entered, you must override the GetVaryByCustomString method in the application's Global.asax file.
The VaryByCustom settings are the same ones used by the VaryByCustom attribute of the @ OutputCache directive.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.