Auto resize image to fill container div
I'm working on a fluid-layout website with two main divs side-by-side at 50% width each. One of these divs is split horizontally with 2 divs at 50% height each. Inside these divs are images or videos which need to fill the container div.
Please see this link for a working example: Click here
Can anyone please tell me what I need to do to achieve this?
Thank you in advance,