var browser = false;
if (document.all && navigator.userAgent.indexOf("Opera") == -1)
 browser = 'ie';
else if (document.getElementById && !document.all)
 browser = 'ns6';
else if (typeof window.opera != 'undefined')
 browser = 'opera';

function popup(url,w_width,w_height,center){
 if(center){
  if(browser=='ie'){
   width = document.body.clientWidth;
   height = document.body.clientHeight;
  }else{
   width = innerWidth;
   height = innerHeight;
  }
  
  x = (width-w_width)/2;
  y = (height-w_height)/2;
  
  var properties = ",left="+x+",top="+y+",screenX="+x+",screenY="+y;
 }
 properties = "width="+w_width+",height="+w_height+",,directories=no,location=no,menubar=no,resizeable=no,scrollbars=yes,status=yes,toolbar=no"+properties;
 window.open(url,'PopUp',properties);
}