A favicon is a small icon in the address bar of browsers. For example when you browse to www.google.com you see the Google icon next to the address bar.
To display a favicon for your site place a 16x16 pixel BMP file named favicon.ico in the root of the site and add the following code to HTML pages:
rel="icon" type="image/vnd.microsoft.icon" href="/favicon.ico" />
Using Non-BMP favicons
To use a non-BMP format file (such as animated GIF or PNG format files) use the following:
gif format should be specified as:
rel="icon" type="image/gif" href="/someimage.gif" />
png format should be specified as
rel="icon" type="image/png" href="/someimage.png" />