How to fix the useless 'favicon.ico page not found' log message?
It's not really a Drupal bug, but a browser bug (I think Firefox might be a culprit)

The best way I found to fix it is to put:

&lt;Location /favicon.ico&gt;
  ErrorDocument 404 "No favicon"
&lt;/Location&gt;


This code should work in your vhost file or should also work in the .htaccess file, see http://httpd.apache.org/docs/2.4/sections.html for more details