[Com]

Зайди сюда и почитай - http://webreference.com/tools/browser/javascript.html
Пример :
<SCRIPT LANGUAGE="JavaScript">
<!--

var bName = navigator.appName;
var bVer = navigator.appVersion;
if (bName == "Netscape")
var browser = "Netscape Navigator"
else
var browser = bName;
document.write("You are currently using ", browser, " ", bVer, ".");

// -->
</SCRIPT