I hope you are well.
404 pages display when someone tries to access a page on your website that doesn't exist.
Our hosting accounts allow you to use your home page as your 404 page, or you can create a custom one.
Note: Server-side scripts, such as PHP, might not work on custom 404 pages because of how web server software (i.e. Apache) handles them.
Thanks for the info @ZulWeb about a 404 error, but this is a 400 error, and it's on GoDaddy's site, not mine.
And the instructions you gave me is where the error takes place. I can't do step 3. I get the 400 error.