Firefox 18 also implements basic support for WebRTC, which will allow browsers to perform video and voice calls without the need for third-party plugins - like Google Chrome.
But it is disabled by default. To enable you have to type about:config in the address bar, accept the warning and search for media.peerconnection.enabled and double-click to change the default value (false) to true.
You also have to change default values to true for
media.navigator.permission.disabledto give automatic access to the browser to the PC’s camera and microphone.
BTW I am personally not sure giving the browser automatic access to mic and camera is a good thing.
But these are all under the hood changes, which the normal user isn’t going to feel. There are a couple of security holes which has been taken care of, and hence upgrading from Firefox 17.0.1 to Firefox 18 wouldn’t be a bad idea.
The release notes are at http://www.mozilla.org/en-US/firefox/18.0/releasenotes/