CSS difference between two pages
I'm new here, and have a quick question I'm trying to make a Magento site and a Wordpress site look the same. To my eye the HTML and css is the same but there seems to be a fundamental difference in the way they are being rendered.
The WP site seems to let divs within other divs overflow - but no amount for FNE or overflow:auto seems to fix it (and these are not present in the Magento one yet it works fine). It seems the problem can be seen in the simple difference between the way header-container is displayed within firebug on the two sites. But I'm all out of ideas!
If anyone could take a quick look at these two sites and tell me what obvious mistake I'm making, I'd be highly grateful.