regions main_prefix and main_suffix block header

I'm gone around and around on this, and I can't seem to see what's going on. I'm new to this theme, and I have everything installed and am using sass, etc. I've created a new subtheme based on the aurora subtheme flavor. I have content in my header and my footer and I've added a custom first sidebar and have content in the content region. But when I go to add content in one of the other regions- the main_prefix or the main_suffix, or I create a new "highlighted" region, when I put content in it, even if just a few words in the ckeditor and save as a block and put the block in that region, the region lays out so the bottom of the region is where I'd expect but the top extends all the way up to the top of the page.

The block looks like it's in the proper place, but if I hover over the wrapping tag in Chrome dev tools, it highlights the whole top of the page. (If I give my block a red bg, the red only shows where I'd expect.) This means the block in the region now overlays my header where my nav links are and I can't click them, een though I can see them. Very strange.

The Chrome dev tool computed css height is from the bottom of the block to the top of the page. I see no other css styles whatsoevercontrolling layout.

I've validated my source. I've checked my template over and over. BTW: I cloned the page.tpl.php from the aurora directory and am using it in my subtheme templates directory. What's going on?

Something else I've noticed is that the header (with id="header") is floated right. I haven't set it to float:right, and can't see any _partial file that's doing that. So what am I missing? When I set it in my _layout.scss file to float none, all the content below jumps up to the top. this is not what I'd expect either as it's a block level element... ?