var xleft;
var xtop;

function CenterWindow(url,  heigth, width)
{
  var xleft=LeftCenter(width);      
  var xtop=TopCenter(heigth); 	  
  var features = "width=" + width + ",height=" + heigth  + ", top=" + xtop + ", left=" + xleft;
  var d_window = window.open(url, "", features);
}

function LeftCenter(l_width)
{
	var ls_width = window.screen.availWidth;
	var xleft = parseInt(ls_width / 2) - parseInt(l_width / 2);
	return xleft
 } 

function TopCenter(t_heigth)
{
	var ts_height = window.screen.availHeight;
	var xtop = parseInt(ts_height/2) - parseInt(t_heigth / 2);
	return xtop
}