It’s helpful during debugging to be able to print out values as the page is executing. Although this is generally done using Response.Write statements, it can also be done with client-side JavaScript. This code can be used to pop up a message box with ASP code, because message boxes themselves are not supported in ASP (server-side code execution). Remember to remove this code segment from the production code; use this only for debugging purposes.
Example:
' ASP code %><%' rest of ASP code