Right there: http://www.aprogrammersjour... The important part is this: application level parameters Application level parameters such as session variables or client side cookies are parameters that are page independent. To cach multiple versions of a page based on application level parameters you can use VarByCustom and the global.asax file. In my case the problem I was faced with was using Forms.Authentication in combination with output caching. If user A logged into my site ......