Short for favorite icon, a customized icon that is used by Microsoft Internet Explorer (IE) versions 5.0 and later. When a user bookmarks a specific Web page, that Web page loads a customized icon into the user's browser, typically a tiny version of a company or Web site's logo. The favicon is displayed next to the Web site's name in the Favorites list and can also be displayed in the Links toolbar. When a site has not created a favicon, IE will load the IE logo into the browser by default.
When a user bookmarks a page, the browser will request a favicon.ico file from the directory of the Web page. If such a file exists, then the Web page is using a favicon and will return the file to the browser.
A typical favicon is 16 x 16 pixels and uses only 16 colors.