Is serving a blank page rather than a 404 error bad for SEO?

Google does indeed call these soft 404s…Soft 404s are a pet peeve of mine.

They are very common, many of the sites I have access to the Google Search Console data for have them.

But they shouldn’t.

If a server can’t return the content the client is requesting, it should inform the client (by returning an error message via HTTP header, not returning a ‘200’ series “success” header).

According to Google, 404s won’t harm your rankings

Regardless, here’s the code from my “default” 404 page:

<h1>Page Not Found</h1>
<p>Something isn't right here, the URL you requested isn't available.</p>
<p>Go to the <a href="https://webmasters.stackexchange.com/">home page</a>.</p>
<p>Try the <a href="http://webmasters.stackexchange.com/sitemap/">sitemap</a>.</p>
<p>Maybe the <a href="https://web.archive.org/">Internet Archive's Wayback Machine</a> has a copy of that page…</p>
<div id="wb404"></div>
<script src="https://archive.org/web/wb404.js"></script>
<p>Or maybe Google can help…</p>
<script> var GOOG_FIXURL_LANG = (navigator.language || '').slice(0,2),GOOG_FIXURL_SITE = location.host; </script>
<script src="https://linkhelp.clients.google.com/tbproxy/lh/wm/fixurl.js"></script>

It’s a bit of overkill but I offer users:

1.) an explanation that the page they requested in unavailable

2.) a link to the home page

3.) a link to the HTML sitemap

4.) a script from archive.org that attempts to show old versions of the page from The Wayback Machine

5.) a Google script that attempts to guess what they were requesting