Divs Overlapping But Only In Firefox

I have been creating a website and the result has been fine in Chrome, IE9, Opera and Safari, BUT in Firefox some of the divs seem to overlap. Here are some screenshots of a very

Solution 1:

It was the float bug. Look at what I did.

jsfiddle.net/pJZ6F/1

Solution 2:

Give header class a property

overflow:hidden;

Hope it helps!!