Ebay uses them. Yahoo uses them. Nearly all of the top websites use "favicons" to help enhance their bookmarks. In a massive list of 200+ bookmarks, your link can quickly become forgotten unless you're using a "favicon".
A favicon (short for favorites icon), also known as a website icon, shortcut icon, url icon, or bookmark icon is an icon associated with a particular website or webpage. A web designer can create such an icon and install it into a website (or webpage) by several means, and most graphical web browsers will then make use of it.
Make your own "favicons" with this great software.