Time for another "common misconceptions and questions" thread!
This article comes from The SEM Post and I think every single newbie SEO in the world will benefit from reading it. Google doesn't crawl to see what is on your 404 pages; no SEO benefit.
Apparently people have been creating custom 404 pages just for the SEO benefits. Now, don't get me wrong - custom 404s can be great! They can provide a better, friendlier user experience. If you link to common or related pages, you can help get people to pages where you want them to go (and where they want to be, which will encourage them to stay and return)!
But those links you put on your 404s? They're not going to make a difference in your ranking. And if you're building links to your custom 404s, God help you.
How did the idea that custom 404 pages would improve your ranking come about? Apparently it's in Google's Quality Rater Guidelines:
Whether you trust what Google says or not is up to you. You can always try running your own tests. But Google says they don't follow any content on pages that return 404s.
Check out their page about custom 404s on Search Console Help. They list several reasons to create good, custom 404 pages. You'll notice that none of them are about manipulating the SERPs or improving your ranking. They're GREAT for your user experience - and that's something you should care about.
I see a lot of newbie questions asking how to fix their 404s, too. I suspect that many of these questions come from newbie freelancers who are working with some kind of "SEO checklist" that they found online, and one of the entries on this checklist is probably "fix as many 404s as possible." Yeah, if you've got a ton of 404s you might want to look at them and figure out why. But more often than not, excessive amounts of 404 pages are symptoms of a larger problem, and not a problem themselves. 404 error pages do not cause any kind of penalty! None!
Check out what Google Search Console Help has to say about fixing 404 errors. Head to the bottom of that page, under "URL error types" and click "Common URL errors" to expand.
The first step is even "decide if it's worth fixing."
Point is, you don't need to freak out about every freakin' 404 ;P
Got thoughts about 404 errors? Custom 404 pages? Tips, criticisms, crazy thoughts? Just wanna vent? Post below!