Google has introduced Crawl Errors feature to help webmasters identify misconfigured smartphone optimized pages on Webmaster Tools. There are several instances where a website shows error page or get redirected to a different & irrelevant page on smartphone. But, desktop users are shown relevant content for the same website.
Googlebot considers these problems as crawl errors, which hurt the user experience of the website. Moreover, these errors are basis of some of the recently announced ranking changes by Google for smartphone search results.
The new Smartphone errors tab introduced will let the Google team will share the list of error pages Googlebot has identified for smartphones.
Some of the errors that will be shared by the team include:
Server errors: When Googlebot got an HTTP error status code while crawling the page.
Not found error and soft 404: Googlebot gets a "not found" message when the page returns an HTTP 404 status code or if the page is detected as soft error page.
Faulty redirects: It is a smartphone specific error that occurs when the smartphone user is redirected to a page irrelevant to the query.
Blocked URLs: Occurs when the robots.txt of the site disallows crawling by Googlebot for smartphones. The disallow directives by such smartphone-specific robots.txt are false and you should check the configuration of your server in case you see a blocked URL reported in Webmaster Tools.Google Brings in Crawl Errors Feature for Smartphone in Webmaster Tools!,