var isIE = navigator.appName.indexOf("Microsoft Internet Explorer");
var isNS = (document.layers);
var isPC = navigator.userAgent.indexOf("Win");

var agt   = navigator.userAgent.toLowerCase();
var vers  = navigator.appVersion.toLowerCase();
var major = parseFloat(navigator.appVersion);
var ie    = (agt.indexOf("msie") != -1);
var ie3   = (ie && (major == 2));
var ie4   = (document.all);
var ie45  = (ie && major >= 4.0 && (parseFloat(vers.substring( vers.indexOf("msie ") + 5, vers.length)) >= 4.5 ));
var ie5  = (ie && major >= 4.0 && (parseFloat(vers.substring( vers.indexOf("msie ") + 5, vers.length)) >= 5.0 ));
var ie55  = (ie && major >= 4.0 && (parseFloat(vers.substring( vers.indexOf("msie ") + 5, vers.length)) >= 5.5 ));
var ns4   = (document.layers);
var ns45  = (ns4 && major>=4.5);
var ns6	  = (!ie && major>=5.0);		// if ns6==true, ns4 and ns45 will both be false, since ns6 behaves differently than ns4/4.5
var win   = (agt.indexOf("win") != -1);
var mac   = (agt.indexOf("mac") != -1);