I've recently put up a few new sites, all with Adsense ads. In all cases, the ads on the home page were not relevant to the content but the ads on internal pages were. Within a few days or, in some cases, a couple of weeks, Google got around to indexing the new site. The home page ads then become relevant. Here's the interesting part. The ads on the new site's home page that were not relevant (before the site got indexed) are the SAME ads as on the home page of the previous site that I had launched (that is now indexed) a week before. In other words, the ads on the new site are relevant to the topic of the previous site. The sites are about completely different topics, not linked together, on different servers, and not in any other way related. The only thing in common is my Google publisher ID and my viewing IP address. This same pattern has occured a number of times now. The point of all this? Don't know. Just interesting.