Duplicate attribute id.

Yeah, it might depend on your subtheme if you get a duplicate ID somewhere in the header, as for the other validation errors frankly this has been discussed before and I have given many reasons why these are for the most part not errors and where they are contentious it has more to do with a failing validator than failing code.

Either you want a theme that works in the real world or some code that passes some esoteric test that a bunch of ivory tower egg heads decided you need pass.