<coolStuff> By Paresh Jagatia </coolStuff>

Once I had a call from my boss saying "Can you tell me if we have used any Favicon file in our website in any page or somewhere? As if we have used it, the file is not in place. Look at this IIS log it is full of 404s for the same file.". And I was absolutely blank about this name. I opened the project and fired "Find in solution" but did not get any FavIcon reference.

Huh, a file that is not referenced anywhere in your website and still your IIS has 404 enteries? Later on I came to know that this is the file that is being shown into the address bar and in the favourites list in most browsers. More information about FavIcon can be found here. And be sure to keep the Favicon file small in size to avoid high bandwidth usage, check this out on Scott's Blog

But keep this file atleast to save 404 in your IIS log. One other file is Robots.txt that, I am not pretty sure, puts 404 in your IIS log when not found by the crawlers. You can check it out.