获取网页元素的绝对位置

       function fGetXY(obj){
           var oTmp = obj;    
           if(!oTmp||(typeOf(oTmp.offsetLeft) == "undefined")
               ||(typeOf(oTmp.offsetTop) == "undefined")
               ||!oTmp.tagName){
                return null;
           }
           var pt = new Point(0,0);  
           do{
      pt.x += oTmp.offsetLeft;
      pt.y += oTmp.offsetTop;
      oTmp = oTmp.offsetParent;
  } while(oTmp.tagName!="BODY");
  return pt;
       }
      
       function Point(iX, iY){
          this.x = iX;
          this.y = iY;
       }