Hundreds of 404 errors are showing up for pages that never existed

[MichaelGregory]

For our site, Google is suddenly reporting hundreds of 404 errors, but the pages they are reporting never existed. The links Google shows are clearly spam style,  but the website hasn't been hacked. This happened a few weeks ago, and after a couple days they disappeared from WMT. What's the deal?

Screen-Shot-2016-02-29-at-9.35.18-AM.png

[KristinaKledzik]

There have been a few people at Moz with similar problems with GSC. People always throw a few ideas around: maybe Google is creating URLs to try to find pages that it can't find through crawling links alone? Maybe another site was trying to hack your site by creating URLs they were hoping would trigger certain content on your site (a laughable idea now, but I remember my college professor showing us a site that put cost parameters in the URL during check out)?

However they got there, though, Eric and Chris gave you some good ways to make sure that you're not still in trouble (if you ever were).

Hope this helps!

[ChrisAshton]

I agree with Eric here so I won't repeat what he has said, simply offer additional suggestions.

Firstly, you can click on each entry from that Crawl Errors window in your screenshot and from the window that pops up, check out the "Linked From" tab. It will show you all the pages this broken one has links from.

If you're having no joy finding them on the pages manually, you can try the Screaming Frog SEO Spider. Crawl the site and if the 404s show up here (if they don't they probably don't exist anymore and you can mark them as "fixed" in Search Console) then click them and check out the "Linked From" tab at the bottom. This tool shows you not only the pages it's linked from but also the anchor text so you can go to the linking pages and use ctrl+f to find the offening link(s).

Hope that helps!

[GlobeRunner]

The 404 errors and other crawl data is provided by a separate database in Google, so the timing of the links and the data you're seeing isn't exactly "in sync" so to speak. I would do a few things--look at the pages to see if there's something on your site that might be causing the errors.

Another option is to look at the link data to see if there are any links pointing to those pages. I would use another source, such as OSE or Majestic.com to see if there are links pointing to those pages that Google isn't reporting (which is often the case).