FIX: The onbeforeunload event unexpectedly occurs when you view a Web page in Internet Explorer 6 on a computer where Windows XP Service Pack 2 or Windows Server 2003 Service Pack 1 is installed

When you view a Web page in Microsoft Internet Explorer 6 on a computer where Microsoft Windows XP with Service Pack 2 (SP2) or Microsoft Windows Server 2003 with Service Pack 1 (SP1) is installed, the onbeforeunload event unexpectedly occurs.

This problem occurs when the Web page streams a file that has the "Content-disposition: attachment" header into an IFRAME element.

Windows XP

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.

Registry information

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

You must create a registry subkey or modify a registry subkey to enable this hotfix. To do this, follow these steps.

Note This hotfix was released together with security update 896688. If security update 896688 is installed, you do not have to create the registry subkey to enable this hotfix.

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey:
   HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl
3. On the Edit menu, point to New, and then click Key.
4. Type FEATURE_NO_ONBEFOREUNLOAD_EVENT_KB905498, and then press ENTER.
5. Click FEATURE_NO_ONBEFOREUNLOAD_EVENT_KB905498.
6. On the Edit menu, point to New, and then click DWORD Value.
7. Type iexplore.exe, and then press ENTER.
8. Click iexplore.exe.
9. On the Edit menu, click Modify.
10. Type 00000001, and then click OK.
11. Exit Registry Editor.

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 item in Control Panel.

Windows Server 2003

Service pack information

To resolve this problem, obtain the latest service pack for Windows Server 2003. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Hotfix information

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 item in Control Panel.

To work around this problem, use the onunload event. For more information about how to use the onunload event, visit the following Microsoft Developer Network (MSDN) Web site:

Microsoft has confirmed that this is a problem in Internet Explorer 6 for Windows XP Service Pack 2 and for Windows Server 2003 Service Pack 1. This problem was first corrected in Windows Server 2003 Service Pack 2.

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: