Portal's HTTP Header includes the lines:

Cache-Control: no-cache
Pragma: no-cache

My first attempt at changing this was to edit the Apache (IHS)
httpd.conf file to load the mod_expires module and set the
Cache-Control max-age to 600 seconds. This worked for html files but
Portal overrides this setting.

Further investigation led me to the portal NavigatorService.properties
file. There I added these lines:

private.expires = 600
private.cache-control: max-age = 600

I Restarted Portal and it still issues the no-cache parameters in the
http header.

There is an old thread in this forum that discusses this but does not
include all the steps to make it happen (one person said they were
successful).

Any ideas?