Microsoft IIS 6.0 [Electronic resources] : Administrators Pocket Consultant نسخه متنی

Customizing Web Server Error Messages

IIS generates HTTP error messages when Web server errors occur. These errors typically pertain to bad client requests, authentication problems, or internal server errors. As the administrator, you have complete control over how error messages are sent back to clients. You can configure IIS to send generic HTTP errors or default custom error files, or you can create your own custom error files.

Understanding Status Codes and Error Messages

Status codes and error messages go hand in hand. Every time a user requests a file on a server, the server generates a status code. The status code indicates the status of the user’s request. If the request succeeds, the status code indicates this, and the requested file is returned to the browser. If the request fails, the status code indicates why, and the server generates an appropriate error message based on this error code. This error message is returned to the browser in place of the requested file.

A status code is a three-digit number that might include a numeric suffix. The first digit of the status code indicates the code’s class. The next two digits indicate the error category, and the suffix (if used) indicates the specific error that occurred. For example, the status code 403 indicates an access forbidden problem, and within this access category a number of specific errors can occur: 403.1 indicates that execute access is denied, 403.2 indicates that read access is denied, and 403.3 indicates that write access is denied.

If you examine the Web server logs or receive an error code while trying to troubleshoot a problem, you’ll see status codes. Table 4-2 shows the general classes for status codes. As you can see from the table, the first digit of the status code provides the key indicator as to what has actually happened. Status codes beginning with 1, 2, or 3 are common and generally don’t indicate a problem. Status codes beginning with 4 or 5 indicate an error and a potential problem that you need to resolve.

Knowing the general problem is helpful when you’re searching through log files or compiling statistics. When you’re troubleshooting or debugging, you need to know the exact error that occurred. Look up that error code in Table 4-3, which provides a listing of the HTTP 1.1 error codes and a brief description of the error.

Managing Custom Error Settings

For each of the standard errors, you can specify how the error is handled. Individual files can have different settings from their parent directory and sites, which means that file settings override directory settings and directory settings override site-wide settings. The following error handling options are available:

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  Default Sends a standard IIS error message to the client.



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  File Sends a customized error file to the client. This option is used with static content.



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  URL Sends a message that redirects the client to a specific URL. This option is used with dynamic content.

Custom files supplied in the standard IIS installation handle most HTTP errors. These files are located in the %SystemRoot%\Help\Iishelp\Common directory. You can edit the default error files directly, or you can create your own files. Be sure to use the File error handling option with static content, such as HTML pages, and the URL type handler with dynamic content, such as .asp pages. If you don’t do this, you might get unexpected results.

The following sections examine how you can view and edit error settings.

Viewing Custom Error Settings

You can view custom error settings by following these steps:

1. 
   

   In the IIS snap-in, right-click the site, directory, or file you want to manage, and then choose Properties.



2. 
   

   Click the Custom Errors tab. As shown in Figure 4-5, you should now see a list of the standard HTTP errors and how they’re handled. Entries are organized by the following categories:

   
   
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     HTTP Error The HTTP status code for the error, which might include a suffix

   
   
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     Type The method used to handle the error (default, file, or URL)

   
   
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     Contents The error text, file path, or URL path associated with the error
     

     
     

     Figure 4-5: The Custom Errors tab shows the error settings for the site, directory, or file you’ve selected for editing.
     

   
   
   
   


3. 
   

   Click OK when you’re finished viewing the error settings.

Editing Custom Error Settings

You can edit custom error settings by completing these steps:

1. 
   

   In the IIS snap-in, right-click the site, directory, or file you want to manage and then choose Properties.



2. 
   

   Click the Custom Errors tab. You should now see a list of the standard HTTP errors and how they’re handled.



3. 
   

   Double-click the entry for the error you want to edit or select the entry and then click Edit. The Edit Custom Error Properties dialog box is displayed, as shown in Figure 4-6.

   
   

   Figure 4-6: The Edit Custom Error Properties dialog box provides an overview of the error and how it’s handled.
   

   
   



4. 
   

   Use the Message Type drop-down list to choose the error handling technique. The options available depend on the type of error and generally include the following:

   
   
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     Default Uses the default error information shown in the Error Code, Sub Error Code, and Definition fields when returning an error message.

   
   
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     File Returns the file specified when the error occurs. Type the complete file path or click Browse to search for the file.

   
   
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     URL Returns the URL specified to the client. Type an absolute URL path for resources on other servers or use a relative URL path for resources on the current server.

   
   
   
   


5. 
   

   Click OK twice.