A Fav Icon is that little icon that appears on the tab of your internet browser next to the name of the site, or the title of the page you’re on. It’s a 16×16 image, usually fairly simple, and it’s a special format (ICO). There aren’t many image editing programs that will save into that format, so I usually use an online tool found at: http://favicon-generator.org/ It’s a free service and you can download your ico file right away. They say that it will resize your image, but I usually make my image 16×16 before I upload it.
Another interesting site someone suggested:
This tool allows you to create favicons from pictures that are up to 5 MB from either JPG, PNG or GIF or even from a gallery. It also lets you generate favicons for different screen sizes and resolutions at the same time.