Webmaster Tools 404 Errors Pages Never Created

[Gyi]

Recently, 196 404 errors appeared in my WMT account for pages that were never created on my site.

Question: Any thoughts on how they got there (i.e. WMT bug, tactic by competitor)?

Question: Thoughts on impact if any?

Question: Thoughts on resolution?

[KeriMorgret]

Run an SEOmoz campaign and look there for the referring URLs?

[Gyi]

Thanks for the responses. Unfortunately, I can't see the referring URL.

[john4math]

Most of the time in GWT you can see the page where the referring link is coming from.  The crawl errors in GWT are links to your site, so if people use an invalid URL to link to your site, it'll show up as a 404 error in GWT.

In my experience when this happens en masse, some spammy site goes a little nuts and tries to link to a bunch of pages, but goofs something up to make the URLs 404s, like putting a extra space which renders as a %20, in the href at the end of the URL.

If it's a common mistake, you might considering putting a rewrite rule in to 301 redirect those 404 URLs to valid pages on your site.  You could also contact the webmaster of that site to fix the URL or URLs that are invalid (especially if it would be a valuable link).  Lastly, you can do nothing and ignore the errors.

[KeriMorgret]

You should be able to see the referring URL for the 404 pages in your GWT account. If someone links to you and does a typo on the end of the URL, or puts your URL in parenthesis and the final ) gets hyperlinked, that can cause a 404.