[Theme: Twenty Eleven] Featured image size

Is there anyway, that I can set the min-width of the page to be the width + a little, of the featured image size?

The reason I ask is because, when I resize my browser and I have a featured image, the featured image often extends past the far right of the browser. This can be seen on this photograph (the image hangs over the border on the right).

How can I stop the featured image overlapping the border on the right?

Thanks for any advice in advance