Valid meta robots content values
Googlebot interprets the following robots meta tag values:

* NOINDEX - prevents the page from being included in the index.
* NOFOLLOW - prevents Googlebot from following any links on the page. (Note that this is different from the link-level NOFOLLOW attribute, which prevents Googlebot from following an individual link.)
* NOARCHIVE - prevents a cached copy of this page from being available in the search results.
* NOSNIPPET - prevents a description from appearing below the page in the search results, as well as prevents caching of the page.
* NOODP - blocks the Open Directory Project description of the page from being used in the description that appears below the page in the search results.
* NONE - equivalent to "NOINDEX, NOFOLLOW".

A word about content value "NONE"
As defined by robotstxt.org, the following direction means NOINDEX, NOFOLLOW.

<META NAME="ROBOTS" CONTENT="NONE">

Don't think I use any of them..