I believe the normal textual content plays a very important part in determining the ads. I have a page about a particular restaurant in a particular city. The title and headers include the word restaurant and the city name, yet I only get 1 ad on the leaderboard format for olive oils. Since I'm describing a visit to this restaurant and mention what dishes we ordered, there is much mention of different foods. The term olive oil is used just once in the text.
where you could specify your specific keywords for the specific page?
With something like that, there is just too much opportunity for publishers to scope out the highest paying keywords that still fit within a generalized theme of the site and use those keywords.
The term olive oil is used just once in the text.
Something to also keep in mind is that the ads are also based upon their own keywords. That particular AdWord could have been targeting keywords anything from "Italian restaurant" to "focaccia bread". So even though you only mention olive oil once, that is probably not the term that AdSense is targeting for your page. A quick search of olive oil shows no shortage of AdWords, so if "olive oil" was actually what was targeted on your page, it should have provided a full leaderboard of ads, not just one.
Your idea for the tag is a good. I've seen it used by other folks. Problem with Google doing it though is that have to get their money worth out of the Applied Semantics purchase :-) I always though that was a less than smart purchase anyway.
mipapage - Correct. I don't use adsense. I have helped others who want use it so I am very familiar with it. I do think that contextual advertising is much better than other forms as I have been helping people test the concept for years. What I have never seen, not even from Applied Semantics, is a solution that is done totally with software work. Comes close to working and works very well as Applied Semantics intended it to work but is not ready yet for the masses as implemented today. If it were than AI would already be here because that's what this needs to do to work everywhere.