When I add an image the picture stretches to fit the screen. The only way I can get the proper dimensions is to delete the Height and Width in the Text area of the Content box.
Here is my website: http://www.hardware-360.com/
Here is a link to what the images do when I don't manually size them in the Text area: http://www.hardware-360.com/ek-working-on-water-block-for-asus-r9-280x-dc-graphics-card/
As you can see the image is stretched