You may notice that Internet Explorer seems to use its local cache differently when you view a Web page that uses frame sets than when you view a Web page that does not use frame sets. This behavior occurs when the frames consist of .asp pages, not .htm pages.

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This behavior occurs because .asp pages are dynamic in nature and the content can change depending on the request. Even though Internet Explorer caches these images internally, Internet Explorer does not send an "If-Modified-Since" header in the image request ("GET") to the server. Therefore, every request causes the Web server to return the image to Internet Explorer, instead of Internet Explorer using a local copy from the local cache.

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A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

   Date     Time    Size      File name   Platform
   -----------------------------------------------------
   2/15/99  2:19pm  2,630 KB  Mshtml.dll  Windows 95/98
   2/15/99  2:17pm  2,360 KB  Mshtml.dll  Windows NT 4.0
				

NOTE: Due to file dependencies, the most recent hotfix or feature that contains the above files may also contain additional files.




The design change in this resolution adds the "If-Modified-Since" header to any image request that uses .asp frames so that the Web server can respond with a "304 Not Modified" response to the image request. Internet Explorer then uses the local copy of the image if the image has already been cached and the image has not changed.

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Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

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