Thumbnail breaking out of div

I’m having trouble keeping a thumbnail image inside a div for a custom page template for a Twenty Twelve child theme

At first I thought it was just the padding, but the image breaks out of it as well when the browser is resized. I’ve tried different things but nothing seems to work.

https://twentyten.info is the test site, it’s the images under the slider.

I’ve added a red test border around the container I need it to stay inside to make it easier to see (that’s why the last image is dropped below the rest)