404 page not found include custom content?

[surenot]

I have many pages that get huge amount of traffic but they are 404 not found so my questions is, since my website is a forum can I display links to newly posted threads whenever URL returns 404.

In other words if a forum or a thread or a post had been deleted the forum will show error message "invalid forum, thread, post" and returns 404 header I would like to show in that page links to new threads?

Will Google index such content? Is this something recommended by SEO experts and accepted by Google?
Thanks

[not2easy]

If you have a way to dynamically update your custom 404 page, sure display links to newly posted threads.

Index? No. Don't block crawling but add a noindex metatag.

[surenot]

Thanks a lot sounds complicated I will juts show 404 error and leave it there don't wanna berry myself deeper into SEO grave

[aakk9999]

When you return 404 header, you can return whatever you want as the content and Google will not index this content.

You should only ever add noindex if the content you are returning with 404 headers can be reached under some different URL that you do not want indexed.

So if you do have means to read the latest thread from the database, returning these with 404 headers will be fine.

[lucy24]

Will Google index such content?

Not if it's on a custom 404 page. Search engines index URLs, not physical pages.* A 404 page by definition has no URL,** since it only appears when a requested URL returns a 404 response.

* Possibly this should be expressed as
Search engines index URLs, not physical pages.

** By the usual yawn-provoking coincidence I was just talking about this in an unrelated thread. If there's been a mistake, the search engine might learn the "real" URL of your custom error pages. For insurance, attach a <noindex> meta to all error documents.