We still have many hundreds of pages with stand-alone Javascript or PHP coding that was put there to rotate some banners just on that page or just on that site or in that directory. Actually we used to have many thousands of pages like that but we sold off some older sites so I don't have to count those anymore.
If I could go back to when we first were putting a lot of those pages out there, I'd definitely tell myself to use a centralized ad management/banner rotator script in almost all cases.
YMMV 'cause the map is not the terrain.
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