var a=document.getElementById("left");
  var b=document.getElementById("right");
  var c=document.getElementById("center");
  if(a.clientHeight>b.clientHeight && a.clientHeight>c.clientHeight)   
  {
  b.style.height=c.style.height=a.clientHeight+"px";
  }
  else if(b.clientHeight>a.clientHeight && b.clientHeight>c.clientHeight) 
  {
  a.style.height=b.clientHeight+"px";
  c.style.height=b.clientHeight+"px";
  }
  else{
  a.style.height=b.style.height=c.clientHeight+"px";
  }