function setbg(){
var con=document.getElementById("topbg");
var ss=document.getElementById("index_index");ss.style.marginTop='48px';
ss.style.zIndex=1;
ss.style.left=(getAbsoluteLeft(con)+10)+'px';
}
var time = null;
function $(Id){return document.getElementById(Id)};
//初始速度
var u=0.5;
//加速度
var a=0.5;
var obj;
function move()
{
   var t=0;
   return function()
   {
   t++;
   s=u*t+0.5*a*t*t;
   this.obj.style.top=s+294;
   if(s>156) {clearTimeout(time);this.obj.style.zIndex=1;}
   };

}
var indexShow=true;
function start(id)
{
var con=document.getElementById("topbg");
if(indexShow)
{
var index=document.getElementById("index_index");
index.style.display='none';

indexShow=false;
}

if(this.obj)
{
this.obj.style.zIndex=-1;
	this.obj.style.display='none';
}
this.obj=$(id);
this.obj.style.display='block';
this.obj.style.left=(getAbsoluteLeft(con)+10)+'px';
time =setInterval(move(),1)
}
//去绝对坐标
function getAbsoluteLeft(ob){
if(!ob){return null;}
    var mendingOb = ob;
    var mendingLeft = mendingOb.offsetLeft;
    while(mendingOb!= null && mendingOb .offsetParent != null && mendingOb .offsetParent.tagName != "BODY" ){
      mendingLeft += mendingOb .offsetParent.offsetLeft;
      mendingOb = mendingOb .offsetParent;
    }
return mendingLeft ;
}