My attempt to use background-clip: content-box is failing. The entire box has a background, including the padding area, not just the content area.
http:
The background CSS property is a one-line way to define all background properties, including background-clip. Thus, specifying background: #ffffd unsets your earlier setting of background-clip. If instead you replace that line with background-color: #ffffd, it should work the way you want it to.
Here's the small modification to your jsfiddle.
This is a common gotcha with shorthand properties in CSS.
Because background-clip is one of the properties that's set by the background shorthand property, your background style is implicitly setting background-clip to border-box (its initial value), overriding your explicit background-clip style:
background-clip: content-box;
background: #ffffd none /* border-box */;
If you move your background-clip declaration beneath background, it'll work as expected:
background: #ffffd none;
background-clip: content-box;
jsFiddle demo