Well difficult to see your source 
To work you will need to set a main div that will have the content and menu.
Then right after the content and menu, and still inside the main div, you put the div with clear-both class.
Like this
Code:
+----------------------------------------+
| +----------+ +-----------------------+ |
| | | | | |
| | menu | | content | |
| | | | | |
| +----------+ +-----------------------+ |
| +------------------------------------+ |
| | clear: both div | |
| +------------------------------------+ |
+---------------------------------------+
I think you missing this in your code, dunno.
ps: cant get this tab/space work on this editor, hope you understand
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