Theoretically, everything I want to do in order to handle different numbers of images in a post is detailed or explained either here or there but for the life of me I’ve reached the limit of being able to follow even the story of the code, and for all my not being a programmer (yes, I know CSS isn’t programming, per se; I’m making a point), everything I’ve ever been able to accomplish is because I’ve been able to follow the story of the code and work from there to enough understanding to get a particular thing done. Not this time, it seems. I’m almost completely lost. This, too, is why I am at sea.

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Addenda

1. For some ungodly and unfathomable reason, the information in that second link regarding the [element]:nth-last-child(6):first-child form is simply not working for me. It is not selecting the first element in a series of six elements.