if (navigator.userAgent.indexOf('Windows') == -1) {
    if (navigator.userAgent.indexOf('Firefox') == -1) {
        document.write('    <link href="MacNNStyle.css" rel="stylesheet" type="text/css" />')
    }
    else {
        document.write('    <link href="MacFFStyle.css" rel="stylesheet" type="text/css" />')
    }
}
else {
    if (navigator.userAgent.indexOf('MSIE') == -1) {
        document.write('    <link href="FFStyle.css" rel="stylesheet" type="text/css" />')
    }
    else {
        document.write('    <link href="Style.css" rel="stylesheet" type="text/css" />')
    }
}

function SwapImage(imagename, imgsrc) {
    document[imagename].src = 'images/' + imgsrc
}