Browser Back Button loses results

Hello,

I am running IIS on Windows Server 2003, and using Index Server to
provide a search function for my website. I am using ASP code (not
..NET).

The search seems to be completed without error, the results are
correctly returned and displayed from the users search, but if they
follow a link returned in the search results, then click the browsers
back button to return to the search results, they receive the error:

'The page cannot be displayed
The page you are looking for is currently unavailable. The Web site
might be experiencing technical difficulties, or you may need to adjust
your browser settings. '

Returning from a .PDF result always seems to return the error:

'Warning: Page has Expired
The page you requested was created using information you submitted in a
form. This page is no longer available. As a security precaution,
Internet Explorer does not automatically resubmit your information for
you.
To resubmit your information and view this Web page, click the Refresh
button. '

and clicking the refresh button correctly returns my results. I cannot
determin any reason know why this is any different to returning from an
..htm or .asp result.

Has anyone got any ideas about this, I have tried several tests, but
all point to everything being OK before the user follows the link away
from the search results.

Any help, hints or just plain guesses would be greatly appreciated.

Thanks in advance

.

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