I have the following background image

How would I use only css to make only 3/4ths of the outer ring visible and selectable like so:
I was able to make only a circle visible and selectable using
a.outer-ring{
-moz-border-radius:100px;
-webkit-border-radius:100px;
border-radius:100px;
However I couldn’t figure out how to remove an inner circle and how to remove 1/4th of the circle (like a pizza slice).
I wholeheartedly wouldn’t recommend it, but http://jsfiddle.net/csswizardry/QLrJj/1/ (clearer: http://jsfiddle.net/csswizardry/QLrJj/)
EDIT: I got quite into this idea; here’s a pretty neat knockout effect http://jsfiddle.net/csswizardry/QLrJj/8/show/ based on this that I wrote http://csswizardry.com/2011/11/create-a-notched-current-state-nav/
H