Favicon (from "favorite icon") is an icon displayed in certain places in web browser, when browsing any webpage supporting favicons. It can be displayed before address in URL bar, on browser tab, in favorites list, etc. This is mostly an icon (
.ico file) in 16x16 or 32x32 dimensions. The easiest way for your website to support it, is to put proper file in root folder of your domain, i.e.
http://en.wikipedia.org/favicon.ico. If you need more fine-grained control over this, then this article should help.
Adding a favicon using HTML uses
<link rel="shortcut icon" href="../../../file.ico" />
<link rel="icon" type="image/x-icon" href="http://en.wikipedia.org/favicon.ico" />
Both methods can be used in the same time.
Some browsers (like Mozilla Firefox and Opera) shows favicon all the time while others (Internet Explorer) only after adding that page to
Favorites folder on Windows.