I've got a asp.internet website. Every single day at, let us say, 8pm the server executes some procedures which last twenty minutes. My real question is: how do i redirect the customers who access this site throughout this time around to a different page around the server? Multithreading?

A smart way is simply to redirect them with respect to the time. Use global.asax and implement the function in Application_BeginRequest method.

Not the very best solution but a simple to apply.

A choice without modifying your application code is to possess a scheduled task that renames the Application_Offline.htm file back and forwards throughout your busy time (Presuming you need to say 'site is busy' or something like that similar)

i.e. at 8pm operate a .softball bat file for example

ren d:\webapp\_App_Offline.htm App_Offline.htm

At 8:20pm run

ren d:\webapp\App_Offline.htm _App_Offline.htm

Not clever, definitely not foolproof but a concept nevertheless that's simple to apply rapidly.