Due to the CSS styling in relation to the dimensions of the JSFiddle Result viewport, the background image is getting cut off.
The 'background-size: cover' property in CSS is scaling and constraining the overall proportional size of the image based on the width of the JSFiddle viewport.
In the body style's background property, using 'center center fixed' centers the image's center point in a fixed position relative to the viewport. If the scaled image is taller than the viewport, it will extend beyond the upper and lower bounds of the JSFiddle Result viewport, resulting in clipping.
To fix this issue, you can try removing 'center center fixed' from the background property on the body style:
body {
background: url("http://f.cl.ly/items/260T100F3j2Y3L1S0g1w/bg.jpg") no-repeat #292929;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}
By doing this, the image will be positioned at the top of the viewport without being clipped along the upper edge. As you narrow the viewport, the image will not be clipped along the bottom once it has resized sufficiently.
If you want to scale your image to fit the available dimensions of the viewport without clipping, consider allowing the image to scale in proportion to the width of the viewport, as suggested in this Answer on Stack Overflow.
If the image content must be fully viewable without clipping, use an 'img' element instead of CSS for positioning the image. This way, the viewport will be scrollable if the image exceeds the viewport's dimensions.
For a demonstration of this alternative approach, you can check out my codepen example.