Favicon

From Site5Wiki

The favicon is the tiny icon used to identify a site quickly in a web browser. It's especially useful to have one for your site in these days of tabbed webbrowsing.

The favicon's file extension is .ico, and it is properly called in the header of your website in this manner:

<link rel="icon" href="http://www.yourdomainname.tld/pathto/favicon.ico" type="image/x-icon" />
<link rel="shortcut icon" href="http://www.yourdomainname.tld/pathto/favicon.ico" type="image/x-icon" />