function addLoadEvent(func){
      var oldonload =window.onload;
      if(typeof window.onload !='function'){
          window.onload =func;
      }else{
          window.onload =function(){
              oldonload();
              func();
          }
      }
  }
     function vMiddle(){
        var middleDiv=document.getElementById("wrap");
        var divHeight=middleDiv.offsetHeight;
        var bodyHeight=document.body.offsetHeight ;
         if(bodyHeight>divHeight){
             middleDiv.style.marginTop=-divHeight/2+"px";
            }
         else{
             middleDiv.style.marginTop=0;
            middleDiv.style.top=0;
             }
    }
 function changHeight(){ 
    var changDiv_1=document.getElementById("savn_1");
    var changDiv_2=document.getElementById("savn_2");
    var changDiv_3=document.getElementById("savn_3");
    var maxheight=Math.max(changDiv_1.scrollHeight,changDiv_2.scrollHeight,changDiv_3.scrollHeight);
    
   
    changDiv_1.style.height=maxheight+'px';
    changDiv_2.style.height=maxheight+'px';
    changDiv_3.style.height=maxheight+'px';
            }
            
    addLoadEvent(vMiddle); 
    addLoadEvent(changHeight);