this is the main div. I changed the color to grey so you can see the change of the css. I have a big margin at the top. none at the sides of my paragraphs though. Also it is just one big container, no columns.

this is the left Div I placed my cursor after the first paragraph and inserted a div in here with 5px margins all around it.

 

this is the right div. This is showing up under the Main div.

The reason is the Main div is collapsing. You add an element to the page athat clears the float and forces the div to not collapse.