register ajax control toolkit in the whole project

Hi,

this site says, that I shoudl put this line in the webconfig, to register ajax control toolkit in the whole projet:

<%@ Register TagPrefix="asp" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit"%>

But if I do it, I get the error: illegal syntax. expecting valid start name character.

How can I then register the toolkit projectwide?