OK, I'll try to make it clear what I mean Imagine I have a website with 3 sections, one for food, one for cars, one for rabbits (I am clearly making this up!). Now, I want to place Adsense blocks on my pages. When the pages load Adsense will know what is on the pages and will serve relevant adverts. Using an ad server, I have the option of creating one block per size once, then delivering it via zones into all the pages, but will that adversely affect Adsense's understanding of the page contents? So, should I: 1] create one ad block, that is served into all the page zones, Adsense will know the pages are different? 2] create three different ad blocks, serving a different block into each of the different sections, potentially so Adsense can more easily target food or cars or rabbits? Did that make sense? The reason is I have a large site with (say) about 200 pages, which I could break down into sections for serving Adsense code ... but at the moment I have used the same piece of code across the whole site. Having spent 120 hours so far and still not got to the end of it, I have it on my "To Do" list to probably go through it all again, using different code "just in case", so I wondered if this was worthwhile. (Yes, I do have a slow sytem, yes I do do code placement manually on pages without software and templates, yes I have over 100 advertisers, yes I am clearly a loony and should have picked something easier to manage).
personally i'd make a new ad block for each niche and allocate a channel to each so you can measure each niches performance
AdSense should still properly detect and display contextual ads when you serve it to each ad zone from one section on your server.