//是否慢动作显示
function checkpopup()
{
   return true;	
}
//显示，参数：对象名，最大高度
function do_it(objname,maxtop)
{
	if ( checkpopup() )
	{	
		var anim = function()
		{
			n += 5;
			if(n >= maxtop){
				document.getElementById(objname).style.marginTop = "0";
				window.clearInterval(t1);
			}else{
				document.getElementById(objname).style.marginTop = "-"+(maxtop - n)+"px";
			}
		},n=0;
		var t1 = window.setInterval(anim,80);
	}
}
//关闭，参数：对象名，最大高度
function close_chk_show(objname,maxtop)
{
	var anim = function()
	{
		n += 5;
		if(n >= maxtop){		
			document.getElementById(objname).style.marginTop = "-"+maxtop+"px";
			window.clearInterval(t1);
		}else{
			document.getElementById(objname).style.marginTop = "-"+ n +"px";
		}
	},n=0;
	var t1 = window.setInterval(anim,80);
}