//browser detection
var userBrowser   = navigator.userAgent; 
var userBrowser   = userBrowser.toLowerCase();
var isExplorer    = userBrowser.indexOf("msie") > -1;
var isNetscape    = userBrowser.indexOf("netscape") > -1; 
var isFirefox     = userBrowser.indexOf("firefox") > -1; 
var isSafari      = userBrowser.indexOf("safari") > -1; 
var isMac         = userBrowser.indexOf("mac") > -1;