A typical 16x16 pixel favicon
A favicon, also known as a page icon, is an icon associated
with a particular website. A web designer can create such an icon,
and many graphical web browsers - such as recent versions of Internet
Explorer, Mozilla, Opera, and Konqueror - can then make use of them.
Browsers that support favicons display them in the browser's address
bar, next to the site's name in lists of bookmarks, and next to
the page's title in a Tabbed Document Interface.
The original means of defining a favicon was by placing a file
called favicon.ico in the root directory of a webserver.
This would then automatically be used in Internet Explorer's favorites
(bookmarks) display. Later, however, a more flexible system was
created, using HTML to indicate the location of an icon for any
given page. This is achieved using a tag of the form <link
rel="shortcut icon" href="favicon.ico">
in the <head> section of the page. In this way, any appropriately
sized image can be used, and although many still use the .ico format,
others use GIF or PNG files.
Most modern browsers implement both methods. Because of this, web
servers receive many request for the file "favicon.ico"
even if it doesn't exist, causing irritation for administrators
looking through their log files.