.grid-12,
.grid-16 {
  margin-right: 0; /* remove 10 pixel right margin so we can add it to the width of the grid */
}

.grid-x {
  display: inline;
  float: left;
  position: relative;
  margin:0;
}
.container-12 .grid-12,
.container-16 .grid-16 {
  width: 950px; /* need to account for dropshadow, there for we add back the right 10 pixel margin. */
}