var newwindow = '';
function popitup(url) 
{
    if (!newwindow.closed && newwindow.location) {
            newwindow.location.href = url;
    } else {
            newwindow=window.open(url,'name',
                            'width=900,height=550,toolbar=yes,directories=yes,status=yes,scrollbars=yes,copyhistory=yes,resizable=yes');
            if (!newwindow.opener) newwindow.opener = self;
    }
    if (window.focus) {newwindow.focus();}
    return false;
}