The shortcut icon, or favicon, is the icon shown by the browser next to a website's address. The browser always tries to use a favicon, even if you didn't specify one. As a result, if that icon is not in browser cache, the browser will request it each time it opens a page on your site. This means that even if you don't care about the shortcut icon itself, it still makes sense to provide one simply to stop the browser from requesting it over and over again.
The shortcut icon is a little image in
ICO format. There are many programs and websites that let you convert a
png image to
ICO format such as http://www.convertico.com.
One way to give the icon to the browser is to name it
favicon.ico and put it in the root folder of your site. ...