I designed the centre section content (where the 'Sale' poster is) - I have no idea other than tables how to lay out my content (I use the free NVU program to generate the html). ...maybe employing somebody to do these bits for me isn't a bad idea!!
Anyhoo, I placed the <BR> before the table in order to prevent the content from overlapping the tabs above when viewed in Chrome.
I will ask my web guys (yes, there are more than 1 - I use an external company for all of my development) to have a look at margin on .content_index - sounds like that may be responsible.
Last thing - when you say wierdness in the css - what have you spotted that doesn't make sense..?
For starters there is a wrapping div with class "frame" that has 0 height and serves no purpose as the child element of .frame is .inner which is positioned absolutely for no reason I can tell either.
In the div .headlinks everything is floated left except div .minicart has a margin to give the links room, then again the table used to position the thing bag and login links.
The "oddness" I mentioned though was all the margins and absolute positioning on the different sections, which I now presume is to position the content before the header and navigation links in the HTML, so okay, I can get behind that kind of a thing for SEO and whatever.
I just found the whole thing is very pixel dependent and a change in the text/copy or the font size could throw the whole layout out of whack in places. But you know it's just a style different than my own, and if it's working, best to ignore me.