@Page: Defines page-specific attributes used by the ASP.NET page parserand compiler. Can   be included only in .aspx files <%@ Page AspCompat="TRUE" language="C#" %> 

@Control:Defines control-specific attributes used by the ASP.NET page parser and   compiler. Can be included only in .ascx files. <%@ Control Language="VB" EnableViewState="false" %>

@Import: Explicitly imports a namespace into a page or user control. The Import   directive cannot have more than one namespace attribute. To import multiple   namespaces,   use multiple @Import directives. <% @ Import Namespace="System.web" %>

@Implements: Indicates that the current page or user control implements the specified .NET   framework interface.<%@ Implements Interface="System.Web.UI.IPostBackEventHandler" %>

@Register: Associates aliases with namespaces and class names for concise notation in   custom server control syntax.<%@ Register Tagprefix="Acme" Tagname="AdRotator" Src="AdRotator.ascx" %>

@Assembly: Links an assembly to the current page during compilation, making all   the   assembly's classes and interfaces available for use on the   page. <%@ Assembly Name="MyAssembly" %><%@ Assembly Src="MySource.vb" %>

@OutputCache: Declaratively controls the output caching policies of an ASP.NET page or a   user control contained in a page<%@ OutputCache Duration="#ofseconds" Location="Any | Client | Downstream | Server | None" Shared="True | False" VaryByControl="controlname" VaryByCustom="browser | customstring" VaryByHeader="headers" VaryByParam="parametername" %>

@Reference: Declaratively indicates that another user control or page source file     should be dynamically compiled and linked against the page in which this directive is   declared.