A favicon, which stands for favorite icon, is a small icon that is displayed in the address bar, next to the URL, and is also used by most browsers when people bookmark your site (or add your site to their favorites). The Apache web server handling your site looks by default for this favicon image in your "www" directory. If the image is not found, it writes an entry to the error log. Not having a favicon has no negative effect on your site in terms of functionality or performance.
For information on adding a favicon to your site, you can refer to this article in our knowledgebase: