div {
width: 150px;
height: 150px;
border: 14px solid red;
border-radius: 50%;
background:
linear-gradient(45deg, transparent, transparent 98px, red 99px, red 113px, transparent 114px, transparent),
linear-gradient(-45deg, transparent, transparent 98px, red 99px, red 113px, transparent 114px, transparent);
}
http://www.youtube.com/watch?v=rWeYwwuNSV0