function open_window(url)
{    
    var browser=navigator.appName.toLowerCase();
        
    var width  = 600;
    var height = 700;
    var left   = (screen.width  - width)/2;
    var top    = (screen.height - height)/2;
    var params = 'width='+width+', height='+height;
    params += ', top='+top+', left='+left;
    
    if (browser=="Microsoft Internet Explorer".toLowerCase())
    {
        newwin = window.open(url,'welcome',
        params+",status=yes,scrollbars=yes,resizable=yes");             
        return false;
    }
    else
    {
        window.open(url,'welcome',        
        params+",status=1,scrollbars=1,resizable=1");        
        return false;
    }
    
    return false;
}