There must, must, must be a property to change a border’s length, to make it shorter (or even longer?) than corner-to-corner.
For instance if you wanted a little line centered over the content, you could do something like
border-top-length: 30%;
border-top-position: center;
The border-length properties should accept any units.
The border-position ones should accept at least left | center | right (or top | center | bottom). You could also specify an offset, like
border-top-position: left 5%;
or
border-top-position: center -10%;
which would shift the border appropriately.
These effects are, s’far as I can tell, very hard to accomplish in an elegant way at the moment. And it seems like something that wouldn’t be //too// big a deal for user agents to implement, as it involves calculations they’re already making for elements’ dimensions.
-LH