DOM:window.navigator

[edit] Summary

Returns a reference to the navigator object, which can be queried for information about the application running the script.

alert("You're using " + navigator.appName);

navigator.appCodeName: Returns the internal "code" name of the current browser.
navigator.appName: Returns the official name of the browser.
navigator.appVersion: Returns the version of the browser as a string.
navigator.buildID: Returns the build identifier of the browser (e.g. "2006090803")
navigator.cookieEnabled: Returns a boolean indicating whether cookies are enabled in the browser or not.
navigator.language: Returns a string representing the language version of the browser.
navigator.mimeTypes: Returns a list of the MIME types supported by the browser.
navigator.onLine: Returns a boolean indicating whether the browser is working online.
navigator.oscpu: Returns a string that represents the current operating system.
navigator.platform: Returns a string representing the platform of the browser.
navigator.plugins: Returns an array of the plugins installed in the browser.
navigator.product: Returns the product name of the current browser. (e.g. "Gecko")
navigator.productSub: Returns the build number of the current browser (e.g. "20060909")
navigator.securityPolicy: Returns an empty string. In Netscape 4.7x, returns "US & CA domestic policy" or "Export policy".
navigator.userAgent: Returns the user agent string for the current browser.
navigator.vendor: Returns the vendor name of the current browser (e.g. "Netscape6")
navigator.vendorSub: Returns the vendor version number (e.g. "6.1")

navigator.javaEnabled: Indicates whether the host browser is Java-enabled or not.
navigator.mozIsLocallyAvailable: Lets code check to see if the document at a given URI is available without using the network.
navigator.preference: Sets a user preference. This method is only available to privileged code, and you should use XPCOM Preferences API instead.
navigator.registerContentHandler: Allows web sites to register themselves as a possible handler for a given MIME type.
navigator.registerProtocolHandler New in Firefox 3: Allows web sites to register themselves as a possible handler for a given protocol.
navigator.taintEnabled Obsolete: Returns false. JavaScript taint/untaint functions removed in JavaScript 1.2[1]

DOM Level 0. Not part of any standard.