In order to create an effective user-centered experience, we create personas for key audience groups. Although a persona is a fictitious representative and may not be exactly like your real end users, the process of creating a persona helps to build empathy for the real people that are going to use the final product.
If you are working on a website redesign, 404s are the very real monsters under your bed. Ignore them, and they will wreak havoc on your website’s traffic. Worst of all, by the time you realize what’s happening it may already be too late.