In Adsense Settings - > My Account - > Scroll to the bottom You will notice "Property Info". AdSense for Content: ca-pub-xxxx AdSense for Search: partner-pub-xxxx The Adsense for content is the regular adsense partner id but where do we use the Adsense for Search id ? Any clues ?
i think its basically just your affiliate id things. i would assume the search id would be for search boxes. i've never used them so i wouldn't know.
The numbers in the "pub-..." are the same for content and search. Google probably wanted to show the users their pub ID without looking in the ads or search code.