Your css is messed up, see
Your container width is too small for the content
.sm-content{ width:700px; }
and you need to float the text content left
.post{margin: 0 1em; width:400px; float: left;}
you can adjust the width as you please but make sure it fits the container. Since your image is floating, the text content isn't so the text container is actually overlapping with the image. If you use inspect in chrome you can see the box layout when you hover over the elements