Robot Meta Tag Options
There are four directives that can be placed in a robots meta tag. The CONTENT section of the meta tag can contain:
index,noindex,follow,nofollow and are separated by commas.
At this point, only the following combinations make sense:

There are also, two global directives that can specify both actions: ALL=INDEX,FOLLOW, and NONE=NOINDEX,NOFOLLOW.

Robots Meta Tag Examples: Importancy: High