function openPopup(url)
{
    var heightScreen = screen.height - 100;
    var topPosition = ((screen.height-600)/2);
    var leftPosition = ((screen.width-800)/2);
    var windowWidth = 800;
    window.open(url, '', 'scrollbars=yes,menubar=no,height='+heightScreen+',width='+windowWidth+',top=100,left='+leftPosition+',resizable=yes,toolbar=no,location=no,status=no');
    return false;
}