var strHTTP_USER_AGENT = navigator.userAgent;

if (strHTTP_USER_AGENT.indexOf("MSIE") != -1) {
    strBROWSER = "ie";
    if (strHTTP_USER_AGENT.indexOf("Mac") != -1)
        strBROWSER = "ie_mac";
} else if (strHTTP_USER_AGENT.indexOf("Mozilla") != -1) {
    strBROWSER = "nn";
    if (strHTTP_USER_AGENT.indexOf("Gecko") != -1)
        strBROWSER = "nn_6";
    if (strHTTP_USER_AGENT.indexOf("Linux") != -1)
        strBROWSER = "nn_linux";
    if (strHTTP_USER_AGENT.indexOf("Mac") != -1)
        strBROWSER = "nn_mac"; 
} else {
    strBROWSER = "__";
}