As first reported in my SEW Columbus presentation (below), Google’s algorithm for matching Content-network-targeted ad groups to Adsense publisher site content treats keywords very differently than Google treats keywords and ad groups directed at the Search network.
The Adsense algorithm works this way: it examines all of the keywords in an ad group, together with the text of the ad(s), and determines a Theme for the ad group. It then displays the ad group’s ads in Adsense units on publisher sites whose content has been determined to match a similar or identical Theme.
So individual keywords in a Content campaign don’t matter; what matters is that they “add up” to a Theme that the algorithm can match to publisher sites’.
This is one of the reasons why only a relatively small number of keywords should be used in Content campaigns. You shouldn’t need more than 30-50 keywords to establish your ad group’s Theme – and in fact, Google tells me that any number or 50 risks “confusing” the algorithm.
This is also another good reason why you should always create separate Content campaigns – i.e., you should have separate campaigns for the Search and Content ad groups – so you can more safely establish Themes and daily budgets for your Content campaigns. More on this in future blog posts.
So what are these mysterious Themes? Google confirmed for me that the Themes match exactly the list of Categories displayed when you’re setting up an AdWords site-targeted campaign.
I’ve listed the categories – all 594 of ’em – in this Microsoft Word file: Google AdWords Content Themes. The “outdented” categories are the Major ones – and each subsequent indented list is a sub- or sub-sub-category.
What can you do with this knowledge? Well, for starters, you should construct your Content ad groups – the keyword lists and ad copy – such that it’s likely that Google’s Adsense algorithm will match the ad group to the Theme you feel best corresponds to your advertised site/product/service.