function dangvanlel(){
var a_div = left.offsetHeight;
var b_div = right.offsetHeight;
var c_div = center.offsetHeight;
if (c_div < a_div || c_div < b_div)
var d_div = -26;
else d_div = 0;
center.style.height = (d_div + Math.max(a_div,b_div,c_div))+"px";
}