I created this quick jsfiddle project to help you help me.
Why does margin-top for #container push the entire body downwards from html when I expect it to push #container from #containerWrapper ?
The idea is to have all the content inside container which would be placed with a margin right under the menu.
This is caused by margin-collapse which happens to two adjacent margins. The inner margin will collapse into the outer one and behaves like the one on the outer container block.
If you want to only apply margin on
#containerWrapper, you could either usepadding-topor put aborderbetween#containerWrapperand its outer block container.