Going through my logs, I've seen this error a few times.
GET /favicon.ico - 404 not found
I just looked into it and found out what it is.
What is a Favicon? Favicon (pronounced fav-eye-con) is short for 'Favorites Icon'
You can customize the Icon(s) in the browsers 'address box window' and 'bookmark listing'. Hence, when people look at their browsers bookmarks they will be drawn to your web page because of the beautiful logo next to your bookmark. Plus when they view your web site. They can confirm that they are viewing your web site by seeing your customized icon(s) in the browser 'address box window'.
This is one place where you can make your own and replace the boring "e" of IE >>