Google Webmaster Tools have again shows great improvement in their system, Now they are able to tell you where did the Not Found or Error 400 came from. The link that they are providing will tell you about the source of the dead link, either it is an internal link error or a link from outside your blog. This is a great help for us webmaster so that we can easily rectify the wrong internal linking that we had made or we can politely ask the source of error about the wrong link that they have towards our blog.
Or we may redirect in order for those wrong url link to be redirected to the proper blog post.
Below photo shows you the number of site either external or internal that is connecting into your site but having a wrong URL.
Upon pressing the number of pages saying Link from the below pictures shows you the different site connected to that wrong URL.
And the below picture gives you an option to Download That table, Download All error for this site, Download all sources of error in this site.
All errors will only be seen if somebody tries to access that link. SO to be able to have a healthy site for your visitor you should always check your Google Webmaster Dashboard and look for any error that you might have.
This is working both in Web Crawl and Mobile Crawl category in the Webmaster’s Tool