Content in Web pages does not appear as expected, or you receive script error messages, after you turn on dynamic HTTP compression for Web sites that use ISAPI filters in Internet Information Services 6.0

When you turn on HTTP compression for dynamic content in Web sites in Microsoft Internet Information Services (IIS) 6.0, you may experience unexpected behavior when you browse Web sites that use an Internet Server API (ISAPI) filter. This problem occurs if the following conditions are true:

• The ISAPI filter registers for the SF_NOTIFY_SEND_RAW_DATA notification and optionally registers for the SF_NOTIFY_SEND_RESPONSE notification.
• The ISAPI Filter buffers the response in the SF_NOTIFY_SEND_RAW_DATA notification and then reinterprets the buffered response to determine whether the response is chunked.

The symptoms that you experience include one or more of the following:

• Content in Web pages does not appear as expected, or you receive script error messages.
• If you are running Microsoft Content Management Server (MCMS) 2002, you receive JavaScript error messages that are similar to the following:
  'NRCOMPAREFROM' is undefined

This problem occurs if the following conditions are true, in the order that they are presented:

1. IIS detects that dynamic compression applies to the response data and then adds the following header fields, as needed:
   • Content-Encoding
   • Vary
   • Transfer-Encoding
2. IIS notifies the SF_NOTIFY_SEND_RESPONSE filters. The SF_NOTIFY_SEND_RESPONSE filters detect the headers that IIS added.
3. IIS starts to send the response and calls the SF_NOTIFY_SEND_RAW_DATA filters.
4. The response is compressed, is chunked, and then is sent to the client.

IIS adds compression headers to the response in step 1. However, the data is not actually modified until step 4. Therefore, when the filter tries to reinterpret the response, filter events that occur between step 1 and step 4 notice that inconsistencies exist between the headers and the body of the response. The headers indicate that the response contains compressed and chunked data. However, the body of the response may or may not be compressed or chunked.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

No prerequisites are required.

Restart requirement

Stop IIS before you apply this hotfix, and then restart IIS after you apply this hotfix.

Note To stop IIS, click Start, click Run, type net stop w3svc in the Open box, and then click OK.

To start IIS after you stop it, click Start, click Run, type net start w3svc in the Open box, and then click OK.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

Windows Server 2003

Windows Server 2003, 64-Bit Edition

To work around this problem, turn off HTTP compression for dynamic content in IIS 6.0 if the Web sites do not require HTTP compression. For more information about how to configure HTTP compression in IIS 6.0, visit the following Microsoft Web site:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base: