var userAgent = navigator.userAgent.toLowerCase();
var isMac = (/macintosh/.test(userAgent));
var lessIE8 = (/msie (6|7)/.test(userAgent));
var isIE8 = (/msie (8)/.test(userAgent));
var isIE = (/msie/.test(userAgent) && !/opera/.test(userAgent));
var isFF = (/mozilla/.test(userAgent) && !/(compatible|webkit)/.test(userAgent));
var isOpera = (/opera/.test( userAgent ));
var isSafari = (/webkit/.test(userAgent));

var isFF4 = (/firefox\/4\./.test(userAgent) && /mozilla/.test(userAgent) && !/(compatible|webkit)/.test(userAgent));
var isFF5 = (/firefox\/5\./.test(userAgent) && /mozilla/.test(userAgent) && !/(compatible|webkit)/.test(userAgent));