// JavaScript Document

function centra(url, width, height, scrollbars) 
   { 
   if (document.all) 
      { 
      var xx = window.screenLeft; 
      var yx = window.screenTop; 
      var wx = window.document.body.offsetWidth; 
      var hx = window.document.body.offsetHeight; 
      } 
  else 
   { 
   var xx = window.screenX; 
   var yx = window.screenY; 
   var wx = window.outerWidth; 
   var hx = window.outerHeight; 
   } 
  var cntx = xx + Math.round((wx - width) / 2); 
  var cnty = yx + Math.round((hx - height) / 2); 
  window.open (url, null, 'left=' + cntx + ',top=' + cnty + ',width=' + 
width + ',height=' + height + ',scrollbars=' + scrollbars); 
}