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Submitted URL: https://support.microsoft.com/help/943891/the-http-status-code-in-iis-7-0-iis-7-5-and-iis-8-0
Effective URL: https://learn.microsoft.com/en-us/troubleshoot/developer/webapps/iis/www-administration-management/http-status-code
Submission: On March 13 via manual from CA — Scanned from CA
Effective URL: https://learn.microsoft.com/en-us/troubleshoot/developer/webapps/iis/www-administration-management/http-status-code
Submission: On March 13 via manual from CA — Scanned from CA
Form analysis 5 forms found in the DOM
Name: site-header-search-form — GET /en-us/search/
<form class="flex-grow-1" method="GET" role="search" id="ms--site-header-search-form" data-bi-name="site-header-search-form" name="site-header-search-form" aria-label="Search" action="/en-us/search/">
<div class="autocomplete display-block" data-bi-name="autocomplete"><!---->
<div class="field-body control ">
<input role="combobox" maxlength="100" aria-autocomplete="list" autocapitalize="off" autocomplete="off" autocorrect="off" spellcheck="false" id="site-header-search-autocomplete-input" data-test-id="site-header-search-autocomplete-input" class="autocomplete-input input input-sm
width-full" type="search" name="terms" aria-expanded="false" aria-owns="ax-0-listbox" aria-controls="ax-0-listbox" aria-activedescendant="" aria-label="Search" aria-describedby="ms--site-header-search-autocomplete-input-description"
placeholder="Search" data-bi-name="site-header-search-autocomplete-input" pattern=".*">
<span aria-hidden="true" class="autocomplete-loader loader has-text-primary " hidden=""></span>
<span hidden="" id="ms--site-header-search-autocomplete-input-description"> Suggestions will filter as you type </span>
</div>
<ul role="listbox" id="ax-0-listbox" data-test-id="site-header-search-autocomplete-input-listbox" class="autocomplete-suggestions is-vertically-scrollable padding-xxs " aria-label="Suggestions" hidden="">
</ul>
<!---->
</div>
<!-- mobile safari will not dispatch submit event unless there's a submit button that is not display:none -->
<button type="submit" class="visually-hidden" tabindex="-1" aria-hidden="true"></button>
<input name="category" hidden="" value="">
</form>Name: site-header-search-form-mobile — GET /en-us/search/
<form class="flex-grow-1" method="GET" role="search" id="ms--site-header-search-form-mobile" data-bi-name="site-header-search-form-mobile" name="site-header-search-form-mobile" aria-label="Search" action="/en-us/search/">
<div class="autocomplete display-block" data-bi-name="autocomplete"><!---->
<div class="field-body control ">
<input role="combobox" maxlength="100" aria-autocomplete="list" autocapitalize="off" autocomplete="off" autocorrect="off" spellcheck="false" id="site-header-search-autocomplete-input-mobile"
data-test-id="site-header-search-autocomplete-input-mobile" class="autocomplete-input input
width-full" type="search" name="terms" aria-expanded="false" aria-owns="ax-1-listbox" aria-controls="ax-1-listbox" aria-activedescendant="" aria-label="Search" aria-describedby="ms--site-header-search-autocomplete-input-mobile-description"
placeholder="Search" data-bi-name="site-header-search-autocomplete-input-mobile" pattern=".*">
<span aria-hidden="true" class="autocomplete-loader loader has-text-primary " hidden=""></span>
<span hidden="" id="ms--site-header-search-autocomplete-input-mobile-description"> Suggestions will filter as you type </span>
</div>
<ul role="listbox" id="ax-1-listbox" data-test-id="site-header-search-autocomplete-input-mobile-listbox" class="autocomplete-suggestions is-vertically-scrollable padding-xxs " aria-label="Suggestions" hidden="">
</ul>
<!---->
</div>
<!-- mobile safari will not dispatch submit event unless there's a submit button that is not display:none -->
<button type="submit" class="visually-hidden" tabindex="-1" aria-hidden="true"></button>
<input name="category" hidden="" value="">
</form>Name: nav-bar-search-form — GET /en-us/search/
<form class="nav-bar-search-form" method="GET" name="nav-bar-search-form" role="search" id="nav-bar-search-form" aria-label="Search" action="/en-us/search/">
<div class="autocomplete" data-bi-name="autocomplete"><!---->
<div class="field-body control ">
<input role="combobox" maxlength="100" aria-autocomplete="list" autocapitalize="off" autocomplete="off" autocorrect="off" spellcheck="false" id="site-search-input" data-test-id="site-search-input" class="autocomplete-input input input-sm
" type="search" name="terms" aria-expanded="false" aria-owns="ax-186-listbox" aria-controls="ax-186-listbox" aria-activedescendant="" aria-label="Search" aria-describedby="ms--site-search-input-description" placeholder="Search" pattern=".*">
<span aria-hidden="true" class="autocomplete-loader loader has-text-primary " hidden=""></span>
<span hidden="" id="ms--site-search-input-description"> Suggestions will filter as you type </span>
</div>
<ul role="listbox" id="ax-186-listbox" data-test-id="site-search-input-listbox" class="autocomplete-suggestions is-vertically-scrollable padding-xxs " aria-label="Suggestions" hidden="">
</ul>
<!---->
</div>
<!-- mobile safari will not dispatch submit event unless there's a submit button that is not display:none -->
<button type="submit" class="visually-hidden" tabindex="-1" aria-hidden="true"></button>
<input name="category" hidden="" value="">
</form>Name: nav-bar-search-form — GET /en-us/search/
<form class="nav-bar-search-form" method="GET" name="nav-bar-search-form" role="search" id="nav-bar-search-form-desktop" aria-label="Search" action="/en-us/search/">
<div class="autocomplete" data-bi-name="autocomplete"><!---->
<div class="field-body control has-icons-left">
<input role="combobox" maxlength="100" aria-autocomplete="list" autocapitalize="off" autocomplete="off" autocorrect="off" spellcheck="false" id="site-search-input-desktop" data-test-id="site-search-input-desktop" class="autocomplete-input input input-sm
control has-icons-left
" type="search" name="terms" aria-expanded="false" aria-owns="ax-187-listbox" aria-controls="ax-187-listbox" aria-activedescendant="" aria-label="Search" aria-describedby="ms--site-search-input-desktop-description" placeholder="Search"
pattern=".*">
<span aria-hidden="true" class="icon is-small is-left">
<span class="has-text-primary docon docon-search"></span>
</span>
<span aria-hidden="true" class="autocomplete-loader loader has-text-primary " hidden=""></span>
<span hidden="" id="ms--site-search-input-desktop-description"> Suggestions will filter as you type </span>
</div>
<ul role="listbox" id="ax-187-listbox" data-test-id="site-search-input-desktop-listbox" class="autocomplete-suggestions is-vertically-scrollable padding-xxs " aria-label="Suggestions" hidden="">
</ul>
<!---->
</div>
<!-- mobile safari will not dispatch submit event unless there's a submit button that is not display:none -->
<button type="submit" class="visually-hidden" tabindex="-1" aria-hidden="true"></button>
<input name="category" hidden="" value="">
</form>javascript:
<form action="javascript:" role="search" aria-label="Search" class="margin-bottom-xxs"><label class="visually-hidden" for="ax-201">Search</label>
<div class="autocomplete display-block" data-bi-name="autocomplete"><!---->
<div class="field-body control has-icons-left">
<input role="combobox" maxlength="100" aria-autocomplete="list" autocapitalize="off" autocomplete="off" autocorrect="off" spellcheck="false" id="ax-201" data-test-id="ax-201" class="autocomplete-input input input-sm
control has-icons-left
width-full" type="text" aria-expanded="false" aria-owns="ax-202-listbox" aria-controls="ax-202-listbox" aria-activedescendant="" aria-describedby="ms--ax-201-description" placeholder="Filter by title" pattern=".*">
<span aria-hidden="true" class="icon is-small is-left">
<span class="has-text-primary docon docon-filter-settings"></span>
</span>
<span aria-hidden="true" class="autocomplete-loader loader has-text-primary " hidden=""></span>
<span hidden="" id="ms--ax-201-description"> Suggestions will filter as you type </span>
</div>
<ul role="listbox" id="ax-202-listbox" data-test-id="ax-201-listbox" class="autocomplete-suggestions is-vertically-scrollable padding-xxs " aria-label="Suggestions" hidden="">
</ul>
<!---->
</div>
</form>Text Content
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Table of contents
HTTP STATUS CODES IN IIS
* Article
* 02/23/2023
* 5 contributors
Feedback
IN THIS ARTICLE
1. Introduction
2. Log file locations
3. HTTP status codes
4. More information
This article provides a list of the Hypertext Transfer Protocol (HTTP) status
codes in Microsoft Internet Information Services (IIS) 7.0 and later versions.
Original product version: Internet Information Services 7.0 and later versions
Original KB number: 943891
INTRODUCTION
When you try to access content on a server that is running IIS by using the HTTP
protocol, IIS returns a numeric code that indicates the result of the request
and semantics of the response, including whether the request was successful.
The first digit of the status code defines the class of response. The last two
digits don't have any categorization role. There are five values for the first
digit:
* 1xx (Informational): Provisional response - the request was received,
continuing process.
* 2xx (Successful): The server successfully received and accepted the request.
* 3xx (Redirection): Further action needs to be taken in order to complete the
request.
* 4xx (Client Error): The request contains an error and can't be fulfilled.
* 5xx (Server Error): The server failed to fulfill the request.
LOG FILE LOCATIONS
The HTTP status code is recorded in the IIS log. IIS 7.0 and later versions put
log files in the following folder by default:
inetpub\logs\Logfiles
This folder contains separate directories for each website. The log files are
created in the directories daily and are named by using the date by default. For
example, a log file may be named as exYYMMDD.log.
HTTP STATUS CODES
This section describes some of the common HTTP status codes.
Note
This article doesn't list every possible HTTP status code as dictated in the
HTTP specification. For example, a custom Internet Server API (ISAPI) filter or
a custom HTTP module can set its own HTTP status code.
1XX - INFORMATIONAL
These HTTP status codes indicate an interim response for communicating request
progress or status before sending a final response to the client computer.
IIS 7.0 and later versions use the following informational HTTP status codes:
Expand table
Code Description Notes 100 Continue Initial part of the request has been
received and has not yet been rejected by the server. The server intends to send
a final response after the request has been fully received and acted upon. 101
Switching protocols Server understands and is willing to comply with client's
request for a change in the application protocol being used.
2XX - SUCCESSFUL
These HTTP status codes indicate that the server successfully received and
accepted the client's request.
IIS 7.0 and later versions use the following success HTTP status codes:
Expand table
Code Description Notes 200 OK The client request was successfully processed. 201
Created The client request has been fulfilled and has resulted in one or more
new resources being created. 202 Accepted The client request has been accepted
for processing, but the processing has not been completed. 203 Nonauthoritative
information The client request was successful but the enclosed content has been
modified from that of the origin server's response. 204 No content The server
has successfully fulfilled the request and that there is no additional content
to send in the response content. 205 Reset content The server has fulfilled the
request and desires that the user agent reset the "document view", which caused
the request to be sent, to its original state as received from the origin
server. 206 Partial content The server is successfully fulfilling a range
request for the target resource by transferring one or more parts of the
selected representation.
3XX - REDIRECTION
These HTTP status codes indicate that the client browser must take more action
to fulfill the request. For example, the client browser may have to request a
different page on the server. Or, the client browser may have to repeat the
request by using a proxy server.
IIS 7.0 and later versions use the following redirection HTTP status codes:
Expand table
Code Description Notes 301 Moved permanently The target resource has been
assigned a new permanent URI and any future references to this resource ought to
use one of the enclosed URIs. 302 Object moved The target resource resides
temporarily under a different URI. Since the redirection might be altered on
occasion, the client ought to continue to use the target URI for future requests
304 Not modified A conditional GET or HEAD request has been received and would
have resulted in a 200 (OK) response if it were not for the fact that the
condition evaluated to false. 307 Temporary redirect The client browser requests
a document that is already in the cache. And the document hasn't been modified
since it was cached. The client browser uses the cached copy of the document
instead of downloading the document from the server.
4XX - CLIENT ERROR
These HTTP status codes indicate that an error has occurred and the client
browser appears to be at fault. For example, the client browser may have
requested a page that doesn't exist. Or, the client browser may not have
provided valid authentication information.
IIS 7.0 and later versions use the following client error HTTP status codes:
Expand table
Code Description Notes 400 Bad request The request could not be understood by
the server due to malformed syntax. The client should not repeat the request
without modifications. For more information, see Troubleshooting HTTP 400 Errors
in IIS. 401 Access denied The request has not been applied because it lacks
valid authentication credentials for the target resource. 403 Forbidden The
server understood the request but refuses to fulfill it. 404 Not found The
origin server didn't find a current representation for the target resource or
isn't willing to disclose that one exists. 405 Method not allowed. The method
received in the request-line is known by the origin server but not supported by
the target resource. 406 Client browser doesn't accept the MIME type of the
requested page. 408 Request timed out The server didn't receive a complete
request message within the time that it was prepared to wait. 412 Precondition
failed. One or more conditions given in the request header fields evaluated to
false when tested on the server.
400 - BAD REQUEST
The Hypertext Transfer Protocol Stack (Http.sys) file blocks IIS 7.0 and later
versions from processing the request because of a problem in the request.
Typically, this HTTP status code means that the request contains invalid
characters or sequences, or that the request goes against the security settings
in the Http.sys file.
IIS 7.0 and later versions define the following HTTP status codes that indicate
a more specific cause of an error 400:
Expand table
Code Description 400.1 Invalid Destination Header 400.2 Invalid Depth Header
400.3 Invalid If Header 400.4 Invalid Overwrite Header 400.5 Invalid Translate
Header 400.6 Invalid Request Body 400.7 Invalid Content Length 400.8 Invalid
Timeout 400.9 Invalid Lock Token
The following HTTP sub-status codes are introduced in IIS 8.0:
Expand table
Code Description 400.10 Invalid X-Forwarded-For (XFF) header 400.11 Invalid
WebSocket request
The following HTTP sub-status codes are introduced in ARR 3.0.1916:
Expand table
Code Description 400.601 Bad client request (ARR) 400.602 Invalid time format
(ARR) 400.603 Parse range error (ARR) 400.604 Client gone (ARR) 400.605 Maximum
number of forwards (ARR) 400.606 Asynchronous competition error (ARR)
401 - ACCESS DENIED
IIS 7.0 and later versions define several HTTP status codes that indicate a more
specific cause of an error 401. The following specific HTTP status codes are
displayed in the client browser but aren't displayed in the IIS log:
Expand table
Code Description Notes 401.1 Logon failed The logon attempt is unsuccessful
probably because of a user name or a password that is invalid. 401.2 Logon
failed due to server configuration This HTTP status code indicates a problem in
the authentication configuration settings on the server. 401.3 Unauthorized due
to ACL on resource This HTTP status code indicates a problem in the NTFS file
system permissions. This problem may occur even if the permissions are correct
for the file that you try to access. For example, this problem occurs if the
IUSR account doesn't have access to the C:\Winnt\System32\Inetsrv directory.
401.4 Authorization failed by filter An Internet Server Application Programming
Interface (ISAPI) filter doesn't let the request be processed because of an
authorization problem. 401.5 Authorization failed by ISAPI/CGI application An
ISAPI application or a Common Gateway Interface (CGI) application doesn't let
the request be processed because of an authorization problem. 401.501 Access
Denied: Too many requests from the same client IP; Dynamic IP Restriction
Concurrent request rate limit reached. 401.502 Forbidden: Too many requests from
the same client IP; Dynamic IP Restriction Maximum request rate limit reached.
401.503 Access Denied: the IP address is included in the Deny list of IP
Restriction 401.504 Access Denied: the host name is included in the Deny list of
IP Restriction
403 - FORBIDDEN
IIS 7.0 and later versions define the following HTTP status codes that indicate
a more specific cause of an error 403:
Expand table
Code Description Notes 403.1 Execute access forbidden The appropriate level of
the Execute permission isn't granted. 403.2 Read access forbidden The
appropriate level of the Read permission isn't granted. Verify that you have set
up IIS 7.0 and later versions to grant the Read permission to the directory.
Additionally, if you use a default document, verify that the default document
exists. 403.3 Write access forbidden The appropriate level of the Write
permission isn't granted. Check the IIS 7.0 and later versions permissions and
the NTFS file system permissions. Make sure that they are set up to grant the
Write permission to the directory. 403.4 SSL required The request is made over a
non-secure channel. But the web application requires a Secure Sockets Layer
(SSL) connection. 403.5 SSL 128 required The server is configured to require a
128-bit SSL connection. But, the request isn't sent by using 128-bit encryption.
403.6 IP address rejected The server is configured to deny access to the current
IP address. 403.7 Client certificate required The server is configured to
require a certificate for client authentication. But the client browser doesn't
have an appropriate client certificate installed. For more information, see HTTP
error 403.7. 403.8 Site access denied The server is configured to deny requests
based on the Domain Name System (DNS) name of the client computer. For more
information, see Dynamic IP Address restrictions. 403.9 Forbidden: too many
clients are trying to connect to the web server 403.10 Forbidden: web server is
configured to deny Execute access 403.11 Forbidden: Password has been changed
403.12 Mapper denied access The page that you want to access requires a client
certificate. But, the user ID that is mapped to the client certificate is denied
access to the file. 403.13 Client certificate revoked The client browser tries
to use a client certificate that was revoked by the issuing certification
authority. 403.14 Directory listing denied The server isn't configured to
display a content directory listing, and a default document isn't set. For more
information, see HTTP Error 403.14. 403.15 Forbidden: Client access licenses
have exceeded limits on the web server 403.16 Client certificate is untrusted or
invalid. The client browser tries to use an invalid client certificate. Or the
server that is running IIS 7.0 and later versions doesn't trust the client
certificate. For more information, see HTTP Error 403.16. 403.17 Client
certificate has expired or is not yet valid. The client browser tries to use a
client certificate that is expired or that isn't yet valid. 403.18 Cannot
execute requested URL in the current application pool. A custom error page is
configured. And the application pool of the customer error page is different
with the application pool of the requested URL. 403.19 Cannot execute CGI
applications for the client browser in this application pool. The identity of
the application pool doesn't have the Replace a process level token user right.
403.20 Forbidden: Passport logon failed 403.21 Forbidden: Source access denied
403.22 Forbidden: Infinite depth is denied 403.501 Forbidden: Too many requests
from the same client IP; Dynamic IP Restriction Concurrent request rate limit
reached 403.502 Forbidden: Too many requests from the same client IP; Dynamic IP
Restriction Maximum request rate limit reached 403.503 Forbidden: the IP address
is included in the Deny list of IP Restriction 403.504 Forbidden: the host name
is included in the Deny list of IP Restriction
404 - NOT FOUND
IIS 7.0 and later versions define the following HTTP status codes that indicate
a more specific cause of an error 404:
Expand table
Code Description Notes 404.0 Not found The file that you try to access is moved
or doesn't exist. 404.1 Site Not Found 404.2 ISAPI or CGI restriction. The
requested ISAPI resource or the requested CGI resource is restricted on the
computer. For more information, see HTTP Error 404.2. 404.3 MIME type
restriction. The current MIME mapping for the requested extension type is
invalid or isn't configured. 404.4 No handler configured. The file name
extension of the requested URL doesn't have a handler that is configured to
process the request on the Web server. 404.5 Denied by request filtering
configuration. The requested URL contains a character sequence that is blocked
by the server. 404.6 Verb denied. The request is made by using an HTTP verb that
isn't configured or that isn't valid. 404.7 File extension denied. The requested
file name extension isn't allowed. 404.8 Hidden namespace. The requested URL is
denied because the directory is hidden. 404.9 Files attribute hidden. The
requested file is hidden. 404.10 Request header too long. The request is denied
because the request headers are too long. 404.11 Request contains double escape
sequence. The request contains a double escape sequence. 404.12 Request contains
high-bit characters. The request contains high-bit characters, and the server is
configured not to allow high-bit characters. 404.13 Content length too large.
The request contains a Content-Length header. The value of the Content-Length
header is larger than the limit that is allowed for the server. For more
information, see HTTP Error 404.13 - CONTENT_LENGTH_TOO_LARGE. 404.14 Request
URL too long. The requested URL exceeds the limit that is allowed for the
server. 404.15 Query string too long. The request contains a query string that
is longer than the limit that is allowed for the server. 404.16 DAV request sent
to the static file handler 404.17 Dynamic content mapped to the static file
handler. For more information, see HTTP Error 404.17 - Not Found. 404.18
Querystring sequence denied 404.19 Denied by filtering rule 404.20 Too Many URL
Segments 404.501 Not Found: Too many requests from the same client IP; Dynamic
IP Restriction Concurrent request rate limit reached 404.502 Not Found: Too many
requests from the same client IP; Dynamic IP Restriction Maximum request rate
limit reached 404.503 Not Found: the IP address is included in the Deny list of
IP Restriction 404.504 Not Found: the host name is included in the Deny list of
IP Restriction
405, 406, 412
Expand table
Code Description Notes 405.0 Method not allowed. The request is made by using an
HTTP method that isn't valid. For more information, see HTTP Error 405.0. 406.0
Invalid MIME type. The request is made by using an Accept header that contains a
MIME value that isn't valid. 412.0 Precondition failed. The request is made by
using an If-Match request header that contains a value that isn't valid.
5XX - SERVER ERROR
The 5xx HTTP status codes indicate that the server can't complete the request
because the server encounters an error.
IIS and later versions use the following server error HTTP status codes:
Expand table
Code Description Notes 500 Internal server error The server encountered an
unexpected condition that prevented it from fulfilling the request. 501 Header
values specify a configuration that is not implemented The server does not
support the functionality required to fulfill the request. 502 Web server
received an invalid response while acting as a gateway or proxy The server,
while acting as a gateway or proxy, received an invalid response from an inbound
server it accessed while attempting to fulfill the request. For more
information, see Troubleshooting 502 Errors in ARR. 503 Service unavailable The
server is currently unable to handle the request due to a temporary overload or
scheduled maintenance, which will likely be alleviated after some delay.
500 - INTERNAL SERVER ERROR
IIS 7.0 and later versions define the following HTTP status codes that indicate
a more specific cause of an error 500:
Expand table
Code Description Notes 500.0 Module or ISAPI error occurred. This HTTP status
code may occur for many server-side reasons. For more information, see HTTP
Error 500.0 - Internal Server Error. 500.11 Application is shutting down on the
web server. The request isn't processed because the destination application pool
is shutting down. Wait for the worker process to finish shutting down, and then
try the request again. If this problem persists, the web application may be
experiencing problems that prevent the web application from shutting down
correctly. 500.12 Application is busy restarting on the web server. The request
isn't processed because the destination application pool is restarting. This
HTTP status code should disappear when you refresh the page. If this HTTP status
code appears again after you refresh the page, the problem may be caused by
antivirus software that is scanning the Global.asa file. If this problem
persists, the web application may be experiencing problems that prevent the web
application from restarting correctly. 500.13 Web server is too busy. The
request isn't processed because the server is too busy to accept any new
incoming requests. Typically, this HTTP status code means that the number of
incoming concurrent requests exceeds the number that the IIS 7.0 and later
versions web application can process. This problem may occur when the
performance configuration settings are set too low, the hardware is
insufficient, or a bottleneck occurs in the IIS 7.0 and later versions web
application. A common troubleshooting method is to generate a memory dump file
of the IIS 7.0 and later versions processes when the error is occurring and then
to debug the memory dump file. 500.15 Direct requests for Global.asax aren't
allowed. A direct request for the Global.asa file or for the Global.asax file is
made. 500.19 Configuration data is invalid. This HTTP status code occurs because
of a problem in the associated applicationhost.config file or in the associated
Web.config file. For more information, see HTTP Error 500.19. 500.21 Module not
recognized. 500.22 An ASP.NET httpModules configuration does not apply in
Managed Pipeline mode. 500.23 An ASP.NET httpHandlers configuration does not
apply in Managed Pipeline mode. 500.24 An ASP.NET impersonation configuration
does not apply in Managed Pipeline mode. 500.50 A rewrite error occurred during
RQ_BEGIN_REQUEST notification handling. A configuration or inbound rule
execution error occurred. Note: Here is where the distributed rules
configuration is read for both inbound and outbound rules. 500.51 A rewrite
error occurred during GL_PRE_BEGIN_REQUEST notification handling. A global
configuration or global rule execution error occurred. Note: Here is where the
global rules configuration is read. 500.52 A rewrite error occurred during
RQ_SEND_RESPONSE notification handling. An outbound rule execution occurred.
500.53 A rewrite error occurred during RQ_RELEASE_REQUEST_STATE notification
handling. An outbound rule execution error occurred. The rule is configured to
be executed before the output user cache gets updated. 500.100 Internal ASP
error. An error occurs during the processing of an Active Server Pages (ASP)
page. To obtain more specific information about the error, disable friendly HTTP
error messages in the web browser. Additionally, the IIS log may show an ASP
error number that corresponds to the error that occurs.
502 - BAD GATEWAY
IIS 7.0 and later versions define the following HTTP status codes that indicate
a more specific cause of an error 502:
Expand table
Code Description 502.1 CGI application timeout. 502.2 Bad gateway: Premature
Exit. 502.3 Bad Gateway: Forwarder Connection Error (ARR). 502.4 Bad Gateway: No
Server (ARR).
The following HTTP status codes are added in ARR 3.0.1916:
Expand table
Code Description 502.2 Map request failure (ARR) 502.3 WinHTTP asynchronous
completion failure (ARR) 502.4 No server (ARR) 502.5 WebSocket failure (ARR)
502.6 Forwarded request failure (ARR) 502.7 Execute request failure (ARR)
503 - SERVICE UNAVAILABLE
IIS 7.0 and later versions define the following HTTP status codes that indicate
a more specific cause of an error 503:
Expand table
Code Description Notes 503.0 Application pool unavailable. The request is sent
to an application pool that is currently stopped or disabled. To resolve this
issue, make sure that the destination application pool is started. The event log
may give information about why the application pool is stopped or disabled.
503.2 Concurrent request limit exceeded. The appConcurrentRequestLimit property
is set to a value that is lower than the current number of concurrent requests.
IIS 7.0 and later versions don't allow more concurrent requests than the value
of the appConcurrentRequestLimit property. 503.3 ASP.NET queue full 503.4
FastCGI queue full
MORE INFORMATION
* HTTP Semantics
* How to Use HTTP Detailed Errors in IIS 7.0
Third-party information disclaimer
The third-party products that this article discusses are manufactured by
companies that are independent of Microsoft. Microsoft makes no warranty,
implied or otherwise, about the performance or reliability of these products.
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