title: does favicon 404 affect performance
body: <p>We have been noticing a lot of 404 errors being thrown in our Coldfusion CFIDE server monitor, and it took us a while to find out that things like missing favicons are causing these errors.</p>
  
  <p>We use a custom 404 template page, which contains some logic to it (more than just basic HTML).  So, whenever a 404 for a favicon occurs, these pages are generated and returned to the user.</p>
  
  <p>Since these favicons are requested by default on many browsers (if there is no  in the header that specifies one, it looks in the site root or something like that), it's throwing massive amounts of 404s on our server, which costs processing time as well as bandwidth for delivery.  Our server runs fine most of the time, but when it does get some heavy usage, we can sometimes have major performance problems.</p>
  
  <p>I know that this is a performance issue, but would it be enough of one to warrant trying to fix this?  If so, is there a way with the Coldfusion server (or our underlying Windows Server 2003 running IIS) to filter what files actually throw a CF 404 error?  Ideally, for files like these favicons, CSS, and Javascript (since a visitor never really "sees" the output of these), we would simply want to return an HTTP 404 response with no content, as it is unneeded...</p>