TwentyFourteen's Image Responsiveness

Hello,

Someone suggested I use TwentyFourteens CSS for image responsiveness. When I put the following code into my custom CSS section it broke my mainpage and my images did not resize!

How do I get my pictures on all my articles, past, present and future to be responsive to all devices?

/**
 * Make sure images with WordPress-added height and width attributes are
 * scaled correctly.
 */

.comment-content img[height],
.entry-content img,
.entry-summary img,
img[class*="align"],
img[class*="wp-image-"],
img[class*="attachment-"],
#site-header img {
	height: auto;
}

img.size-full,
img.size-large,
.wp-post-image,
.post-thumbnail img {
	height: auto;
	max-width: 100%;
}