Div not sticking to bottom at low viewport heights

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CSS3

HTML5

http://i.imgur.com/4r2oHAM.png[^]
In the image above, the div that's highlighted is expected to stick to the bottom at all times and under all circumstances, but when dev tools are launched or window height is decreased manually, the window becomes scrollable, and upon scrolling to the bottom, the div moves up and it looks creepy. The styles for the div concerned are visible in dev tools. Help appreciated.

What I have tried:

I tried setting min-height for html and body, but didn't change that behavior. I've tried changing that to fixed but didn't yield the results I was looking for.