Google couldn't access your site because your DNS server did not respond to the request in a timely manner.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

Check with your registrar to make sure your site is correctly set up and that your server is connected to the Internet.

Google couldn't access your site because your DNS server did not recognize your hostname (such as www.example.com).

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

Check with your registrar to make sure your site is correctly set up and that your server is connected to the Internet.

The server timed out waiting for the request.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

It's possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

Google was able to connect to your server, but it closed the connection before full headers were sent. Please check back later.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

It's possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

Your server successfully processed Google's request, but isn't returning any content because the connection with the server was reset. Please check back later.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

It's possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

Your server closed the connection before we could receive a full response, and the body of the response appears to be truncated.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

It's possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

Google couldn't access your site because your server refused the connection. Your hosting provider may be blocking Googlebot, or there may be a problem with the configuration of their firewall.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

It's possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

Google wasn't able to connect to your server because the network is unreachable or down.

It's possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Google is generally able to access your site properly.

Google was unable to connect to your server.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Googlebot is generally able to access your site properly.

Check that your server is connected to the Internet. It's also possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

Google was able to connect to your server, but the connection was closed before the server sent any data.

Use Fetch as Google to check if Googlebot can currently crawl your site. If Fetch as Google returns the content of your homepage without problems, you can assume that Googlebot is generally able to access your site properly.

It’s possible that your server is overloaded or misconfigured. If the problem persists, check with your hosting provider.

When you see this kind of error for your URLs, it means that Googlebot couldn't access your URL, the request timed out, or your site was busy. As a result, Googlebot was forced to abandon the request.

Read more about server connectivity errors.

Usually, when a visitor requests a page on your site that doesn't exist, a web server returns a 404 (not found) error. This HTTP response code clearly tells both browsers and search engines that the page doesn't exist. As a result, the content of the page (if any) won't be crawled or indexed by search engines.

A soft 404 occurs when your server returns a real page for a URL that doesn't actually exist on your site. This usually happens when your server handles faulty or non-existent URLs as "OK," and redirects the user to a valid page like the home page or a "custom" 404 page.  

This is a problem because search engines might spend much of their time crawling and indexing non-existent, often duplicative URLs on your site. This can negatively impact your site's crawl coverage because your real, unique URLs might not be discovered as quickly or visited as frequently due to the time Googlebot spends on non-existent pages.

If your page is truly gone and has no replacement, we recommend that you configure your server to always return either a 404 (Not found) or a 410 (Gone) response code in response to a request for a non-existing page. You can improve your visitors' experience by setting up a custom 404 page when returning a 404 response code. For example, you could create a page containing a list of your most popular pages, or a link to your home page, or a feedback link. But it's important to remember that it's not enough to just create a page that displays a 404 message. You also need to return the correct 404 or 410 HTTP response code.

Googlebot requested a URL that doesn't exist on your site.

Fixing 404 errors

Most 404 errors don't affect your site's ranking in Google, so you can safely ignore them. Typically, they are caused by typos, site misconfigurations, or by Google's increased efforts to recognize and crawl links in embedded content such as JavaScript. Here are some pointers to help you investigate and fix 404 errors:

1. Decide if it's worth fixing. Many (most?) 404 errors are not worth fixing. Here's why:Sort your 404s by priority and fix the ones that need to be fixed. You can ignore the other ones, because 404s don't harm your site's indexing or ranking.
   • If it is a deleted page that has no replacement or equivalent, returning a 404 is the right thing to do.
   • If it is a bad URL generated by a script, or that never have existed on your site, it's probably not a problem you need to worry about. It might bother you to see it on your report, but you don't need to fix it, unless the URL is a commonly misspelled link (see below).
2. See where the invalid links live. Click a URL to see Linked from these pages information. Your fix will depend on whether the link is coming from your own or from another site:
   1. Fix links from your own site to missing pages, or delete them if appropriate.
      • If the content has moved, add a redirect.
      • If you have permanently deleted content without intending to replace it with newer, related content, let the old URL return a 404 or 410. Currently Google treats 410s (Gone) the same as 404s (Not found). Returning a code other than 404 or 410 for a non-existent page (or redirecting users to another page, such as the homepage, instead of returning a 404) can be problematic. Such pages are called soft 404s, and can be confusing to both users and search engines.
      • If the URL is unknown: You might occasionally see 404 errors for URLs that never existed on your site. These unexpected URLs might be generated by Googlebot trying to follow links found in JavaScript, Flash files, or other embedded content, or possibly that exist only in a sitemap. For example, your site may use code like this to track file downloads in Google Analytics:

        
          Hello World PDF

        When Googlebot  sees this code, it might try to crawl the URL http://www.example.com/download-helloworld, even though it's not a real page. In this case, the link may appear as a 404 (Not Found) error in the Crawl Errors report. Google is working to prevent this type of crawl error. This error has no effect on the crawling or ranking of your site.

   2. Fix misspelled links from other sites with 301 redirects. For example, a misspelling of a legitimate URL (www.example.com/redshoos instead of www.example.com/redshoes) probably happened when someone linking to your site simply made a typo. In this case, you can capture that misspelled URL by creating a 301 redirect to the correct URL. You can also contact the webmaster of a site with an incorrect link, and ask for the link to be updated or removed.
3. Ignore the rest of the errors. Don't create fake content, redirect to your homepage, or use robots.txt to block those URLs—all of these things make it harder for us to recognize your site’s structure and process it properly. We call these soft 404 errors. Note that clicking This issue is fixed in the Crawl Errors report only temporarily hides the 404 error; the error will reappear the next time Google tries to crawl that URL. (Once Google has successfully crawled a URL, it can try to crawl that URL forever. Issuing a 300-level redirect will delay the recrawl attempt, possibly for a very long time.)  Note that submitting a URL removal request using the URL removal tool will not remove the error from this report.

If you don't recognize a URL on your site, you can ignore it. These errors occur when someone browses to a non-existent URL on your site - perhaps someone mistyped a URL in the browser, or someone mistyped a link URL. However, you might want to catch some of these mistyped URLs as described in the list above.

In general, Google discovers content by following links from one page to another. To crawl a page, Googlebot must be able to access it. If you're seeing unexpected Access Denied errors, it may be for the following reasons:

• Googlebot couldn't access a URL on your site because your site requires users to log in to view all or some of your content.
• Your server requires users to authenticate using a proxy, or your hosting provider may be blocking Google from accessing your site.

To fix:

• Test that your robots.txt is working as expected and does not block Google. The Test robots.txt tool lets you see exactly how Googlebot will interpret the contents of your robots.txt file. The Google user-agent is Googlebot. 
• Use Fetch as Google to understand exactly how your site appears to Googlebot. This can be very useful when troubleshooting problems with your site's content or discoverability in search results.

Not followed errors lists URLs that Google could not completely follow, along with some information as to why. Here are some reasons why Googlebot may not have been able to follow URLs on your site:

Flash, JavaScript, active content

Some features such as JavaScript, cookies, session IDs, frames, DHTML, or Flash can make it difficult for search engines to crawl your site. Check the following:

• Use a text browser such as Lynx to examine your site, since many search engines see your site much as Lynx would. If features such as JavaScript, cookies, session IDs, frames, DHTML, or Flash keep you from seeing all of your site in a text browser, then search engine spiders may have trouble crawling your site.
• Use Fetch as Google to see exactly how your site appears to Google.
• If you use dynamic pages (for instance, if your URL contains a ? character), be aware that not all search engine spiders crawl dynamic and static pages. In general, we recommend keeping parameters short and using them sparingly. If you're confident about how parameters work for your site, you can tell Google how we should handle them.

Redirects

• If you are permanently redirecting from one page to another, make sure you're returning the right HTTP status code (301 Moved Permanently).
• Where possible, use absolute rather than relative links. (For instance, when linking to another page in your site, link to www.example.com/mypage.html rather than simply mypage.html).
• Try to make every page on your site reachable from at least one static text link. In general, minimize the number of redirects needed to follow a link from one page to another.
• Check your redirects point to the right pages! Sometimes we discover redirects that point to themselves (resulting in a loop error) or to invalid URLs.
• Don't include redirected URLs in your Sitemaps.
• Keep your URLs as short as possible. Make sure you aren't automatically appending information (such as session IDs) to your redirect URLs.
• Make sure your site allows search bots to crawl your site without session IDs or arguments that track their path through the site.

When you see this error for URLs, it means that Googlebot could either not communicate with the DNS server, or your server had no entry for your site.

Read more about DNS errors.

The Faulty redirect error appears in the URL Errors section of the Crawl > Crawl Errors page under the Smartphones tab.

Some websites use separate URLs to serve desktop and smartphone users and configure desktop pages to direct smartphone users to the mobile site (e.g. m.example.com). A faulty redirect occurs when a desktop page incorrectly redirects smartphone users to a smartphone page not relevant to their query. A typical example of this occurs when all desktop pages redirect smartphone users to the homepage of the smartphone-optimized site. In the figure below, the redirects shown with red arrows indicate faulty redirects:

This kind of redirect disrupts users' workflow and can cause them to stop using the site and look elsewhere.

Following are some tips to help you create a mobile-friendly search experience and avoid faulty redirects:

• Do a few searches on your own phone (or set your browser to act like a smartphone) to see how your site behaves.
• Use the example URLs provided in the report as a starting point to debug exactly where the problem is with your server configuration.
• Set up your server so that it redirects smartphone users to the equivalent URL on your smartphone site.
• If a page on your site doesn't have a smartphone equivalent, keep users on the desktop page, rather than redirecting them to the smartphone site's homepage. Doing nothing is better than doing something wrong in this case.
• Consider using responsive web design, which serves the same content for desktop and smartphone users.
• Finally, read our recommendations for having separate URLs for desktop and smartphone users.

The "Blocked" error appears on the Smartphone tab of the URL Errors section of the Crawl > Crawl Errors page. If you get the "Blocked" error for a URL on your site, that means that the URL is blocked for Google's smartphone Googlebot in your site's robots.txt file.

This may not necessarily be a smartphone-specific error (for example, the equivalent desktop pages may also be blocked). However, it often indicates that the robots.txt file needs to be modified to allow crawling of smartphone-enabled URLs. When the smartphone-enabled URLs are blocked, the mobile pages can't be crawled and because of this, they may not appear in search results.

If you get the "Blocked" smartphone crawl error for URLs on your site, examine your site's robots.txt file and make sure that you are not inadvertently blocking parts of your site from being crawled by Googlebot for smartphones.

For more information, see our recommendations.

The Flash content error appears in the URL Errors section of the Crawl > Crawl Errors page under the Smartphones tab.

Our algorithms list URLs in this section as having content rendered mostly in Flash. Many devices cannot render these pages because Flash is not supported by iOS or Android versions 4.1 and higher.

Whichever approach you take to address this issue, be sure to allow Googlebot access to all assets of your site (CSS, JavaScript, and images) and do not block them with robots.txt or by other means. Our algorithms need these external files to detect your site's design configuration and treat it appropriately. You can make sure our indexing algorithms have access to your site by using the Fetch as Google feature in Search Console.