//清除cooike
function clearCookies(name)
{
    function display(str)
    {
        document.getElementById("list_last_question").style.display="none";
    };	
    try{
	    var url="sub/ajax.aspx?act=clearCookies&name="+name;
	    var ai=new ajax_operation(url,display,1);
		ai.doGet();
		return false;
    }
    catch(error){
    return false;
    };
}