IIS ignores If-Modified-Since (1985) and sends 304

From: Larry Weisberg (lweisberg_at_finjan.com)
Date: 09/07/04 

Date: Tue, 7 Sep 2004 21:59:42 +0300

I have an application which modifies certain browser requests as follows:
1) IE requests http://www.server.com/page.html (page.html is last modified
today, e.g.)
2) MyApp requests page.html from www.server.com, modifies content in such a
way that there is a pop-up in the returned page with a submit button. MyApp
also modifies the Last-Modified field to be some date in 1985
3) User presses push button, which calls myApp (basically a proxy) directly
4) my App returns a META refresh to go to page
http://www.server.com/page.html
5) IE issues a GET http://www.server.com/page.html and, indeed, sends a
header If-Modified-Since with a value exactly corresponding to the 1985 date
in the Last-Modified tag in step #2
6) MyApp sends the request with the same headers to www.server.com along
with the If-Modified-Since 1985.
7) IIS (the www.server.com is really my own PC running IIS) returns a 304,
rather than returning the content of page.html, even though page.html is
certainly newer than 1985.

Any ideas why? And what I might do (in the headers I send in Step #2) to
force IIS in the end to return the entire page and NOT a 304?

Thanks,
Larry