var _POPUP_FEATURES = 'location=0,status=yes,toolbar=yes,menubar=yes,width=800,height=600,left=50,top=50,scrollbars=yes,resizable=yes';

function raw_popup(url, target, features) {
    if (isUndefined(features)) features = _POPUP_FEATURES;
    if (isUndefined(target  )) target   = '_blank';
    var theWindow = window.open(url, target, features);
    theWindow.focus();
    return theWindow;
}

function link_popup(src, features) {
    return raw_popup(src.getAttribute('href'), src.getAttribute('target') || '_blank', features);
}
function isUndefined(v) {
    var undef;
    return v===undef;
}

// code taken from "Accessible Pop-up Links" by Caio Chassot at www.alistapart.com