var timer = 10;   //计时器时钟
var HeightEnd=240;//Div高度
var aNum = 20;   //步进速度
var isOpen = false;//层状态 打开还是关闭 默认关闭
function $(name){return document.getElementById(name);}
function voids() {
setTimeout("extend()",66);
}


// 展开/关闭
function extend(){
var tHeight = parseInt(gs($("box"),"height"));
if(!isOpen){
   $("box").style.display="block";
   if (tHeight<HeightEnd){
    $("box").style.height=(tHeight+aNum)+"px";
    $("box").filters.alpha.opacity+=3;
    setTimeout("extend()",timer);
   }else{
    isOpen=true; //打开状态
    $("box").filters.alpha.opacity=100;
	setTimeout( "voids('box')", 5000 ); 
	
   }
}else{
   if((tHeight-aNum)>0){
    $("box").style.height=(tHeight-aNum)+"px";
    $("box").filters.alpha.opacity-=5;
    setTimeout("extend()",timer);
   }else{
    isOpen=false; //关闭状态
    $("box").style.display="none";
    $("tabTop").innerHTML = "展开";
    $("box").filters.alpha.opacity=2;
   }
}
}

function gs(d,a){
if (d.currentStyle){ 
    var curVal=d.currentStyle[a]
}else{ 
    var curVal=document.defaultView.getComputedStyle(d, null)[a]
} 
return curVal;
}