If you've analyzed your server logs closely, you may have noticed that these 404's are produced only by Internet Explorer 5. It's a new feature which can
be very nice for the visitor but a headache for those webmasters who don't know about it yet. So what's going on here?
When a visitor wants to put your page in their Favorites with IE5, this browser starts looking for an icon file called 'favicon.ico'.
If it's not found, that will result in a 404 'not found' error. So: lots of 404's for 'favicon.ico' means lots of people are bookmarking your pages. That's
good, isn't it? But you'd better avoid all those errors.
If the icon is found, it will be downloaded, and used to mark the file that was bookmarked in the browser. Instead of the normal
"internet document" icon in the Favorites menu. the visitor will see yours.
When the page is loaded in the browser, it will also appear in front of the URL in the Address field. Makes your site stand out!
Microsoft calls this a shortcut icon. They have a page in their MSDN section describing
how to set this up
- but that page doesn't tell
you all. I have a few extra tips for you.