Inner shadow produces nice soft darkened edges not unlike photoshop inner shadow layer style

inner_shadow.css

/* x-pos, y-pos*, blur, spread, #color */

.box_shadow {
  -webkit-box-shadow: inset 0px 0px 10px 0px #222;  /* WebKit */
  -moz-box-shadow:    inset 0px 0px 10px 0px #222;  /* Firefox */
  box-shadow:         inset 0px 0px 10px 0px #222;  /* Standard */
}