A favicon is a small image (16 x 16 pixels) that appears alongside the url address of the browser’s address bar.

Favicons will also appear beside a browser’s “favourite” url listing when a site with favicon is bookmarked as show below:

Creating a favicon
You can create a small image (16 x 16 pixels) using Fireworks,  Photoshop or GIMP and then use IrfanView to convert the image to .ico format. In this case, you must save the file as favicon.ico or it will not work.
Add favicon to your blog
Upload your favicon.ico file to …