Sometimes you really want to know if your site reports a 404 error. For newbies it may sound strange but here is guide on how to find "Error 404" on your blog post.

Google webmaster tools is the best options to find out 404 server errors. If you are registered with GWT, you can view the list of 404 errors that the Googlebot has come across.

Now Bing also have a Webmaster tool as Google has, from there you will also be able to find 404 errors

If you want to verify if your site is reporting a 404 then Xenu may be a good tool to use, if you would like to discover which page links to a 404 you can put some strings with php e.g (domain.com/404?uri=URI_WHICH_GAVE_ERROR&from=REFERRER_INTERNAL_URL)
this will show in your analytics as soon as someone see it.

You can also use the 404 Notifier plugin, which is able to notify you via email or RSS feed whenever a 404 error is found

Use Broken Link Checker... Generally you don't have to worry much about 404.

See how to fix it @http://getblogtutorial..com.ng/2016/09/how-to-find-404-error.html