step1 Login to your cPanel.
step2 Under the Files section, click on File Manager.
step3 Click on public_html.
step4 From the top left-hand menu, click on New File.
step5 Under New File Name: type in 404.html then click Create New File.
step6 Right-click on the newly created 404.html then click on Edit.
step7 In the Text Editor pop-up, simply click on Edit.
step8 Now you'd want to type in the HTML code for your custom 404 page, in this example we're using a very basic one that you
can copy if you'd like. However you can get very fancy with your own, even going so far as to copying the style and
images of your main site and placing your error message in the middle of that.
<html>
<head>
<title>404 Page Not Found</title>
<body>
<H2>We're sorry but the page you're looking for could not be found</H2>
</body>
</html>
step9 After you've made your edits, click on Save Changes, and you should see a green Success pop-up.
step10 Now if you directly try to pull up /404.html in your web-browser, you should see the page we just created.