Http Cache test "Private" fails

Description:
1) Save attachment onto desktop and open it.
2) "Private 1A" page is loaded.
3) Clear the cache.
4) Click Link1.
5) Note the Timestamp and go back.
6) Click Link2 immediately.
7) The time stamps are different.

Expected Result:Time Stamps from Link1 & Link2 should be same
Actual Result:Time Stamps from Link1 & Link2 are different

Observered:This test passes on Opera 9.64 on linux,IE 6.0 on windows,Opera 9.64
on windows,Chrome 1.0 on Windowsand fails on Safari 4,Firefox(both on Windows &
Linux)