网页退后过期的实现

        <META http-equiv="Expires" content="0"/>
		<META http-equiv="Cache-Control" content="no-store, no-cache, must-revalidate"/>  
		<META http-equiv="Pragma" content="no-cache"/> 
			<%
			response.setHeader("Pragma","no-cache"); 
			response.setHeader("Cache-Control","no-store, no-cache, must-revalidate"); 
			response.setDateHeader("Expires", 0);
			%>