HTTP Error Codes

I. Summary
When a user tries to access content on a server that is running Internet information Services (IIS) through HTTP or File Transfer Protocol (FTP), IIS returns a numeric code that represents the status of the request. This status code is logged in the IIS log and may also be displayed in a Web browser or FTP client. The status code can indicate whether a specific request has succeeded, and can reveal the exact cause of the request failure.
More information
The location of the log file. By default, IIS places its log files in the%windir\system32\logfiles folder. Each World Wide Web (WWW) site and an FTP site have a separate directory in that directory. By default, log files are created every day in these directories, and the log file is named with the date (for example, ExYYMMDD.log).

Second, error message
1XX-Informational Tips
These status codes represent a temporary response. The client should be prepared to receive one or more 1xx responses before receiving a regular response.

100-Continue.
101-Switch protocol.

2XX-Success
This type of status code indicates that the server successfully accepted the client request.

200-OK. The client request was successful.
201-created.
202-accepted.
203-Non-authoritative information.
204-no content.
205-Reset the content.
206-Partial content.

3xx-redirect
The client browser must take more action to implement the request. For example, the browser might have to request a different page on the server, or repeat the request through a proxy server.

301-moved permanently The document requested by the customer elsewhere, the new URL is given in the location header, and the browser should automatically access the new URL.
302-found is similar to 301, but the new URL should be treated as a temporary replacement, not a permanent. Note that the corresponding status information in HTTP1.0 is "Moved temporatily", and when the status code appears, the browser can automatically access the new URL, so it is a useful status code. Note that this status code can sometimes be used with 301 substitutions. For example, if the browser mistakenly requests Http://host/~user (the trailing slash is missing), some servers return 301, and some return 302. Strictly speaking, we can only assume that the browser will automatically redirect only if the original request is get. See 307.

    303-see Other is similar to 301/302, except that if the original request is post,location, the redirect target document specified by the header should be fetched via get (HTTP 1.1 new).   the
    304-not Modified Client has a buffered document and makes a conditional request (typically a document that provides a if-modified-since header that the customer only wants to update than the specified date). The server tells the customer that the original buffered document can continue to be used. The documents requested by the
    305-use Proxy client should be extracted from the proxy server indicated by the location header (HTTP 1.1 is new).
    307-temporary Redirect and 302 (Found) are the same. Many browsers incorrectly respond to a 302 response for redirection, even if the original request is post, even though it can actually be redirected only if the answer to the POST request is 303. For this reason, HTTP 1.1 has been added in 307 to allow for more cleanup of the region in several status codes: When a 303 response occurs, the browser can follow the redirected get and post requests, and if the 307 answer, the browser can only follow the redirect to the GET request. (HTTP 1.1 new)

4xx-Client Error
An error occurred and the client appears to be having problems. For example, a client requests a page that does not exist, and the client does not provide valid authentication information.  
    400-Bad request.  
    401-access is denied. IIS defines a number of different 401 errors, which indicate a more specific cause of the error. These specific error codes are displayed in the browser, but are not displayed in the IIS log:     

401.1-Login failed.
401.2-The server configuration caused the login to fail.
401.3-not authorized due to ACL restrictions on resources.
401.4-Filter Authorization failed.
401.5-ISAPI/CGI application authorization failed.
401.7– access is denied by the URL authorization policy on the WEB server. This error code is specific to IIS 6.0.

403-Forbidden: IIS defines a number of different 403 errors that indicate a more specific cause of the error:

403.1-execution access is forbidden.
403.2-Read access is forbidden.
403.3-Write access is forbidden.
403.4-Requires SSL.
403.5-Requires SSL 128.
The 403.6-IP address is rejected.
403.7-Requires a client certificate.
403.8-site access is denied.
403.9-Excessive number of users.
403.10-Invalid configuration.
403.11-Password change.
403.12-Deny access to the mapping table.
403.13-The client certificate is revoked.
403.14-Reject directory list.
403.15-Client access permission exceeded.
403.16-Client certificate is not trusted or invalid.
403.17-The client certificate has expired or is not yet valid.
403.18-The requested URL cannot be executed in the current application pool. This error code is specific to IIS 6.0.
403.19-CGI cannot be executed for clients in this application pool. This error code is specific to IIS 6.0.
403.20-passport Login failed. This error code is specific to IIS 6.0.

404-not found.

404.0-(None) – No files or directories found.
404.1-Unable to access the WEB site on the requested port.
The 404.2-web service extension lockout policy blocks this request.
The 404.3-mime mapping policy blocks this request.

405-The HTTP verb used to access this page is not allowed (method not allowed)
406-The client browser does not accept the MIME type of the requested page.
407-proxy authentication is required.
412-Precondition failed.
413– request entity is too large.
414-The request URI is too long.
415– media types not supported.
The range requested by 416– is not sufficient.
417– execution failed.
423– a locked error.

5XX-Server Error
The server could not complete the request because it encountered an error.

500-Internal server error.

500.12-The application is busy restarting on the WEB server.
The 500.13-web server is too busy.
500.15-Direct Request Global.asa is not allowed.
500.16–unc authorization credentials are incorrect. This error code is specific to IIS 6.0.
The 500.18–url authorization store cannot be opened. This error code is specific to IIS 6.0.
500.100-Internal ASP error.

501-The header value specifies the configuration that is not implemented.
An invalid response was received when the 502-web server was used as a gateway or proxy server.

The 502.1-cgi application timed out.
502.2-CGI Application error. Application.

503-The service is not available. This error code is specific to IIS 6.0.
504-The gateway timed out.
505-http version is not supported.

HTTP Error Codes