As far as I understood it...
When Google is to rank a page on a website, it considers the content on this specific page (and backlinks and so on...) and counts the keywords.
So, page X would rank for Xs keywords while page Y for Ys, while the landing page would rank for the landing page's keywords.
When I look into webmaster tools, the main keywords for my whole site seem to be those from some sub-page with lots of content, while the landing page's keywords occur to be less important.
So: Does Google look at all the content of a site to find the keywords for the landing page?
I'd be really glad if someone could confirm this!
I'd have to review my SEO then...