var ns4 = document.layers;
var op5 = (navigator.userAgent.indexOf("Opera 5") != -1) || (navigator.userAgent.indexOf("Opera/5") != -1);
var op6 = (navigator.userAgent.indexOf("Opera 6") != -1) || (navigator.userAgent.indexOf("Opera/6") != -1);
var opera = (navigator.userAgent.indexOf("Opera") != -1);
var agt = navigator.userAgent.toLowerCase();
var mac = (agt.indexOf("mac") != -1);
var ie = (agt.indexOf("msie") != -1);
var mac_ie = mac && ie;