<!-- 
function centra(url, width, height) { 
if (document.all) { 
var x = window.screenLeft; 
var y = window.screenTop; 
var w = window.document.body.offsetWidth; 
var h = window.document.body.offsetHeight; 
} 
else { 
var x = window.screenX; 
var y = window.screenY; 
var w = window.outerWidth; 
var h = window.outerHeight; 
} 
var cntx = x + Math.round((w - width) / 2); 
var cnty = y + Math.round((h - height) / 2); 
window.open (url, null, 'left=' + cntx + ',top=' + cnty + ',width=' + 
width + ',height=' + height +',scrollbars=0'); 
} 
//-->