  <h1 align="center"><b>Robozilla</b> Error Codes</h1>
       
<table border="0">
  <tr> 
          
    <td> 
      <div align="center"><b><a href="#connection">Connection Errors</a></b> 
            </div>
            <ul>
              <li><a href="#-0">-<b>0 - Unknown Error</b></a></li>
              <li><b><a href="#-1">-1 - Unable to Resolve Host</a></b></li>
              <li><b><a href="#-4">-4 - Can't Connect </a></b></li>
              <li><a href="#-5"><b>-5 - Timeout</b></a></li>
              <li><b><a href="#-6">-6 - Bad URL</a></b></li>
              <li><a href="#-7"><b>-7 - Server Error</b></a></li>
            </ul>
            <div align="center"><b><a href="#redirection">300: Redirection</a></b> 
            </div>
            <ul>
              <li><b><a href="#303">303 See Other</a></b></li>
              <li><b><a href="#302">302</a></b></li>
              <li><b><a href="#301">301</a></b></li>
              <li><b><a href="#300">300</a></b></li>
            </ul>
          </td>
          
    <td> 
      <div align="center"><b><a href="#client">400: Client errors</a></b> 
            </div>
            <ul>
              <li><a href="#417"><b>417 Expectation Failed</b></a></li>
              <li><b><a href="#416">416 Requested Range Not Satisfiable</a></b></li>
              <li><b><a href="#415">415 Unsupported Media Type</a></b></li>
              <li><b><a href="#414">414 Request-URI Too Large</a></b></li>
              <li><b><a href="#413">413 Request Entity Too Large</a></b></li>
              <li><b><a href="#412">412 Precondition Failed</a></b></li>
              <li><b><a href="#411">411 Length Required</a></b></li>
              <li><b><a href="#410">410 Gone</a></b></li>
              <li><b><a href="#409">409 Conflict</a></b></li>
              <li><b><a href="#408">408 Request Time-Out</a></b></li>
              <li><b><a href="#407">407 Proxy Authentication Required</a></b></li>
              <li><b><a href="#406">406 Not Acceptable</a></b></li>
              <li><b><a href="#405">405 Method Not Allowed</a></b></li>
              <li><a href="#404"><b>404 Not Found</b></a></li>
              <li><b><a href="#403">403 Forbidden</a></b></li>
              <li><b><a href="#402">402 Payment Required</a></b></li>
              <li><b><a href="#401">401 Unauthorised</a></b></li>
              <li><b><a href="#400">400 Bad Request</a></b></li>
            </ul>
          </td>
          
    <td> 
      <div align="center"><b><a href="#server">500: Server errors</a></b> 
            </div>
            <ul>
              <li><b><a href="#505">505 HTTP Version Not Supported</a></b></li>
              <li><b><a href="#504">504 Gateway Timeout</a></b></li>
              <li><b><a href="#503">503 Server Overload</a></b></li>
              <li><b><a href="#502">502 Bad Gateway</a></b></li>
              <li><b><a href="#501">501 Not Implemented</a></b> </li>
              <li><b><a href="#500">500 Server error</a></b></li>
            </ul>
          </td>
        </tr>
      </table>
      
  
<p align="center">A list of error codes that can be returned by <a href="/ddp/06014/">Robozilla</a>, 
  the automated link checker. </p>
  <h3><b><a name="connection"></a></b>Connection Errors</h3>
      <ul>
        <li> <b><a name="-0"></a>-0 - Unknown Error</b><br>
          Errors of this type are usually DNS errors. This means that a nslookup 
          of the web site resulted in a zero response; the site's domain name 
          could not be resolved. As Robozilla checks each link twice before flagging 
          it red, such a site is unlikely to come back. It is worth searching 
          for keywords from the site's URL/title on a search engine, to try to 
          locate a new URL for the site. </li>
        <li><a name="-1"></a><b>-1 - Unable to Resolve Host</b><br>
          Common causes include a typo in the host name, and non-payment of domain 
          name charges. Firstly, check to see if there are any obvious typos in 
          the host name. If so, fix them, and then try the URL again. You may 
          wish to do a whois query on the domain name. Using a service such as 
          allwhois.com, query the name in question and check when the name was 
          due for re-registration. </li>
        <li><b><a name="-4"></a>-4 - Can't connect </b><br>
          The server exists, but it is not allowing connections on the HTTP port. 
          This generally suggests the server is wrongly configured, and as such 
          the best recourse is normally to unreview the URL and check back later. 
        </li>
        <li><a name="-5"></a><b>-5 - Timeout</b><br>
          Robozilla connected OK, and sent the request but timed out waiting to 
          fetch the page. This happens sometimes on really busy servers. If this 
          error is still present when you come to check the URL it suggests the 
          site may be down for a long period of time. </li>
        <li><b><a name="-6"></a>-6 - Bad URL<br>
          </b>There was a problem with the format of the URL. Perhaps http:// 
          is missing? Note: when you click on the [edit] link for a URL missing 
          http://, the edit page for the site comes up with http:// helpfully 
          attached by the dmoz software, and the URL link therefore works. You 
          still have to click Update (not "This URL works for me") in order for 
          the update to take effect. Else, check for other examples of incorrect 
          syntax. For instance: <br>
          htttp://www.example.com/<br>
          htp://www.example.com/<br>
          http:://www.example.com/ <br>
          http://w.example.com/ </li>
        <li><b><a name="-7"></a>-7 - Server error</b><br>
          The server returned an unknown error code, and is probably misconfigured. 
          The page may still show up okay, but it's a good idea to check it just 
          in case. </li>
      </ul>
      <center>
        <div align="left"> 
          
      <h3><b><a name="redirection"></a>300: Redirection</b></h3>
        </div>
      </center>
      <ul>
        <li> 
          <center>
            <div align="left"> <b><a name="303"></a>303 See Other</b><br>
              The page has a new URL. Update the listing to the new URL. </div>
          </center>
        </li>
        <li> 
          <center>
            <div align="left"><b><a name="302"></a>302</b><br>
              Redirect Temporarily The page has a new URL temporarily (in theory; 
              in practice, this is often used as a synonym for code 301). Update 
              the listing to the new URL.</div>
          </center>
        </li>
        <li> 
          <center>
            <div align="left"><b><a name="301"></a>301</b><br>
              Redirect Permanently The page has a new URL. Update the listing 
              to the new URL. </div>
          </center>
        </li>
        <li> 
          <center>
            <div align="left"> 
              <p><b><a name="300"></a>300</b><br>
                Moved The page has moved to one of several possibilities. Pick 
                the one that's closest to the original page, and update the URL. 
              </p>
            </div>
          </center>
        </li>
      </ul>
      <center>
        <div align="left"> 
          
      <h3><b><a name="client"></a></b>400: Client errors </h3>
        </div>
      </center>
      <ul>
        <li><a name="417"></a><b>417 Expectation Failed</b><br>
          The expectation given in an Expect request-header field could not be 
          met by this server. Should never happen to Robozilla.</li>
        <li><b><a name="416"></a>416 Requested Range Not Satisfiable</b><br>
          A browser which sends information on acceptable file size as part of 
          its request, has requested a file that does not fit these parameters. 
          Since Robozilla does not send this header, this shouldn't happen unless 
          the server is misconfigured.</li>
        <li> <b><a name="415"></a>415 Unsupported Media Type</b><br>
          The server is refusing to service the request because the entity of 
          the request is in a format not supported by the requested resource for 
          the requested method. Back up a few levels and see if there's an alternate 
          version of the page you're looking for.</li>
        <li> <b><a name="414"></a>414 Request-URI Too Large</b> <br>
          The URL (usually created by a GET form request) is too large for the 
          server to handle. Check to see that a lot of garbage didn't somehow 
          get pasted in after the URL.</li>
        <li> <b><a name="413"></a>413 Request Entity Too Large</b> <br>
          The server is refusing to process a request because the request entity 
          is larger than the server is willing or able to process. Should never 
          occur for Robozilla.</li>
        <li><a name="412"></a> <b>412 Precondition Failed</b> <br>
          The precondition given in one or more of the request-header fields evaluated 
          to false when it was tested on the server. Should never occur for Robozilla.</li>
        <li> <b><a name="411"></a>411 Length Required</b><br>
          The server requires a content-length in the request. Should never occur 
          for Robozilla.</li>
        <li> <b><a name="410"></a>410 Gone</b> <br>
          The resource doesn't exist at all. The page was removed by the webmaster. 
          This page should be deleted. </li>
        <li><b><a name="409"></a>409 Conflict</b><br>
          The request could not be completed due to a conflict with the current 
          state of the resource. Typically indicates defective programming of 
          the Web server. </li>
        <li> <b><a name="408"></a>408 Request Time-Out</b><br>
          The server took longer than expected to return a page, and timed out. 
          Similar to -5, but generated by the server, rather than Robozilla. </li>
        <li><b><a name="407"></a>407 Proxy Authentication Required</b><br>
          This code is similar to 401 (Unauthorised), but indicates that the client 
          must first authenticate itself with the proxy. Since Robozilla doesn't 
          use a proxy, this should never occur unless on a faulty server. </li>
        <li><a name="406"></a><b>406 Not Acceptable</b><br>
          The server cannot generate a response that the requestor is willing 
          to accept.</li>
        <li> <b><a name="405"></a>405 Method Not Allowed</b><br>
          Usually happens when a CGI script doesn't allow GET requests any longer. 
          Backtrack the URL and see if you can find another way to show the data.</li>
        <li> <b><a name="404"></a>404 Not Found</b><br>
          The resource doesn't exist on this server. The page was probably removed. 
        </li>
        <li><b><a name="403"></a>403 Forbidden</b><br>
          You can't see this resource on the server. The admin may have turned 
          off the pages because of load or for some other reason.</li>
        <li><a name="402"></a> <b>402 Payment Required</b><br>
          This resource cannot be accessed without payment.</li>
        <li> <b><a name="401"></a>401 Unauthorised</b><br>
          You can't see this resource on the server. Perhaps a password is now 
          required, or the resource you're looking for has moved.</li>
        <li><a name="400"></a> <b>400 Bad Request</b><br>
          Usually occurs due to a space in the URL or other malformed URL syntax. 
          Try converting spaces to %20 and see if that fixes the error. </li>
      </ul>
      <ul>
      </ul>
      
  <h3><b><a name="server"></a></b>500: Server errors</h3>
      <ul>
        <li> <b><a name="505"></a>505 HTTP Version Not Supported<br>
          </b> The server does not support the HTTP protocol version that was 
          used in the request message. Should never happen with Robozilla; if 
          it does, the server might be misconfigured.</li>
        <li> <b><a name="504"></a>504 Gateway Timeout</b> <br>
          A server being used by this server has not responded in time. </li>
        <li><a name="503"></a><b>503 Server Overload</b><br>
          Service temporarily overloaded. The server cannot process the request 
          due to a high load. </li>
        <li><b><a name="502"></a>502 Bad Gateway</b> <br>
          The server, while acting as a gateway or proxy, received an invalid 
          response from the upstream server it accessed in attempting to fulfill 
          the request. Might be transient; hold for a few days and see if it clears 
          up.</li>
        <li> <b><a name="501"></a>501 Not Implemented</b><br>
          Function not implemented in Web server software. Might occur when a 
          site is moved to a different platform (operating system). Look for an 
          updated URL. </li>
        <li><b><a name="500"></a>500 Server error</b><br>
          Sometimes happens due to a server misconfiguration. Usually this is 
          transient, and goes away, but check first. </li>
      </ul>
