[html5] Offline Cache: files not listed in manifest

[Brenton Strine]

Why is it that files which are not mentioned in the manifest disappear
from the page after you reload?

I have four images being displayed on a page, and my manifest looks like this:

CACHE MANIFEST

CACHE:
img1.png

NETWORK:
img2.png

FALLBACK:
img3.png img1.png

When online, all four images load the first time. But if I refresh,
the 4th image, which is not mentioned, breaks. Why is this?

Brenton