if ((navigator.appVersion.indexOf("Mac") != -1)) { // Mac
document.write("<script type='text/JavaScript' language='JavaScript' src='/js/message1.js'></script>");
}

else if ((navigator.appName.indexOf("Netscape") != -1)) { // Windows NN
document.write("<script type='text/JavaScript' language='JavaScript' src='/js/message2.js'></script>");
}

else { // Windows IE
document.write("<script type='text/JavaScript' language='JavaScript' src='/js/message2.js'></script>");
}