innerhtml控件,该如何解决

innerhtml控件
模仿做了一个展开的js，但是怎样把这个折叠起来？
<SCRIPT   language=javascript>
function   op(id,Coupon_ID,account_name,pid,amount)
{
  var   total=document.getElementById( "total ").value;
  for(i=1;i <=total;i++)
  {
    document.getElementById( "E_ "+i).innerHTML= " ";
  }
var   url= "history.asp?id= "+Coupon_ID;
var   xmlhttp=new   ActiveXObject( "microsoft.xmlhttp ");
xmlhttp.open( "POST ",url,false);
xmlhttp.send(null);
document.getElementById( "E_ "+id).innerHTML= " <%=Coupon_alert1%> ： <br> "+amount+ " <br> ---------- <br> <%=Coupon_alert2%> <br> "+xmlhttp.responseText;
}


------解决方案--------------------
document.getElementById(...).style.display = "none ";
document.getElementById(...).style.display = " ";