Customizing error pages in Web Content Management

Problem
When using IBM Web Content Management (WCM), there is no way to change the error pages if 404 errors are returned. For example, when using servlet rendering to render a website, if you try to request a URL that doesn't exist, you are presented with a 404 error.
Is it possible to display a customer page with this error?

Resolving the problem
You can bypass Portal's default behavior by implementing a solution using servlet filters to return custom error pages.
One example of how to implement this solution is covered in detail on the Portal Family Wiki as Custom Error Pages.