function popup(url, target)
{
        w = screen.width*(3/4);
        h = screen.height*(3/4);
        l = (screen.width-w)/2;
        t = (screen.height-h)/2;
        widthHeight = "width="+w+",height="+h+",left="+l+",top="+t+",menubar=no,resizable=yes,scrollbars=no,status=no,toolbar=no,location=no";
        window.open(url,target,widthHeight);
        return true
}

function openchat(oForm)
{
        if (oForm.nick.value.length == 0)
        {
                alert ('You have to fill in a nickname');
        }
        else
        {
                s = oForm.style.value + '?nick=' + oForm.nick.value;
                popup(s,'chatroom');
        }
        return false;
}