function openPopupWindow(url,name,width,height,posX,posY)
{
    var sFeatures = 'status=no,toolbar=no,menubar=no,location=no,resizable=yes,scrollbars=0,width='+width+',height='+height;
    
    if(posX==null)
    {
        var leftPos = (screen.width - width) / 2;
        var topPos = (screen.height - height) / 2;
       
        sFeatures += ',left='+leftPos+',top='+topPos;
    }
    else
        sFeatures += ',left='+posX+',top='+posY;
        
    return window.open(url,name,sFeatures,true);
}

function tellFriend()
{
    var url = encodeURIComponent(document.location.href);    
    openPopupWindow('/inne/PowiadomZnajomego.aspx?Url='+url,'preview',500,290,null,null);    
}