function volo(url, width, height) { 
var cntx = (screen.width - width) / 2; 
var cnty = (screen.height - height) / 2; 
window.open(url, 'null', 'left=' + cntx + ',top=' + cnty + ',width=' + width + ',height=' + height +',scrollbars=no'); 
} 
function catalogo(url, width, height) { 
var cntx = (screen.width - width) / 2; 
var cnty = (screen.height - height) / 2; 
window.open(url, 'null', 'left=' + cntx + ',top=' + cnty + ',width=' + width + ',height=' + height +',scrollbars=no'); 
} 
function transfer(url, width, height) { 
var cntx = (screen.width - width) / 2; 
var cnty = (screen.height - height) / 2; 
window.open(url, 'null', 'left=' + cntx + ',top=' + cnty + ',width=' + width + ',height=' + height +',scrollbars=no'); 
} 
function offerte(url, width, height) { 
var cntx = (screen.width - width) / 2; 
var cnty = (screen.height - height) / 2; 
window.open(url, 'null', 'left=' + cntx + ',top=' + cnty + ',width=' + width + ',height=' + height +',scrollbars=no'); 
} 
function voli(url, width, height) { 
var cntx = (screen.width - width) / 2; 
var cnty = (screen.height - height) / 2; 
window.open(url, 'null', 'left=' + cntx + ',top=' + cnty + ',width=' + width + ',height=' + height +',scrollbars=no'); 
}