First, I want you to open this file and take a look at it: 404.txt. This page is not that hard to understand, considering it’s similar with page.php, index.php and single.php. Thyere are only a few codes. This file will get your visitor a message when you have a broken link. You can write whatever you want here.
It starts with the code that will will 404.php to header.php and ends with the code that will link 404.php to footer.php. In the middle of it, we have the title and the styling for the content. Also, we have there the message you want to show. It’s really simple to customize this page. Also we have the ending div for the content div we started in header.php.