Difference between SITE: & CACHE: Google Results

[FreeThemer]

During my little play time I take each day I was looking at sites in google and found something that I found strange.

So I went to a site and then used the google toolbar to check the google cache:

cache: [Only Registered users can see links . Click Here To Register...]

And the page was cached. However then I did:

site: [Only Registered users can see links . Click Here To Register...]

it returned no results?

Can anyone shed some light on this? How can it be in google cache but not index? Does that mean that backlinks would not count from that page?

[Spiral]

Cache shows the cache copy of that page by google.
Whereas "site" displays the number of pages indexed by google from that site ,So "site" can't be used for a webpage.It's used for a website/domain ..So your command should be "site:themers.org"