How to display 404 page

Review:
https://codex.www.ads-software.com/Creating_an_Error_404_Page

Ok, maybe I was not being very clear. I don’t want to create a 404 page. I installed theme Twenty Twelve. I does have a 404 page of its own, but the browser is not displaying it. How do I get the theme’s 404 page to show up? Thank you.

In the form of:

//yoursite.com/some_random_text_that_does_not_exist

What happens if you try something simple, like mydomain.com/404

It still shows that same browser default page: “Not Found

The requested URL /wordpress/404 was not found on this server.”

sounds like it’s not pinging your htaccess file, or the settings need reset. Try re-saving permalinks.

Ok… sorry but I’m kinda new to this. So I assume I can do that by going to Permalinks and hit “Save Changes”?

Exactly

Ok, I did and tried the “404” string again and it still doesn’t show up.

If you are trying to use a custom 404 Page, you need to consult theme provider. Otherwise, that is the basic 404 page you are seeing.

Make sure you have some form of pretty links set. Go to your permalinks and chose post-name or some other option other than the default.

some time my website have trouble error 404 page
https://diachiso.vn/ha-noi/home.html

@vuvhiep,
Start your own topic instead of posting on someone’s ongoing thread:
https://www.ads-software.com/support/forum/how-to-and-troubleshooting#postform