We’ve released a new WordPress plugin to help reduce the server load that can occasionally result from a large number of 404 requests on a WordPress-powered site. I wrote about this issue in some detail previously.
This plugin gives you the ability to set a collection of file extensions that you do not want WordPress to handle. For example, a request to a .gif file probably isn’t a valid request to one of your posts or pages, so having WordPress look at the URL and try to find something to show is a waste of server resources.
Note that this is a very basic implementation that has been only lightly tested on a few sites. If you have any trouble with it or think an alternate implementation would be an improvement, patches and/or suggestions are quite welcome.
All of my plugins now have new homes on the Crowd Favorite website, along with their own dedicated community support forum. You can find the details, screenshots, support info, etc. for this plugin on the Exclude File Type Requests plugin page.