Imagine-all those different diagrams, all composed of the exact same componets, and all springing from the exact same source. and if you could map the entire internet you would see how each page influences each other page. The base template for the very first website being improved with new tags. Those tags being replicated in new websites and other websites with other new tags springing from there. Imagine when the very first website that incorporated an IMG tag. The tree that would spring from there would be huge. Then further down there'd be overlap between that and the basic HREf linking tag.
There might be an analogy here.