function screen_properties() {
    yourConf = screen.width + "x" + screen.height + " pixels, " + screen.pixelDepth +" bit depth, " + screen.colorDepth + " bit color palette depth.";
    return yourConf;
}

if ((screen.width < 1024) || (screen.pixelDepth < 8) || (screen.colorDepth < 8)) {
    alert("This site looks best with minimum 1024x768 screen resolution and 8 bit color depth. Your settings are: " + screen_properties());
}