Using the last-child selector

Another solution that might work for you is to reverse the relationship. So you would set the border for all list items. You would then use first-child to eliminate the border for the first item. The first-child is statically supported in all browsers (meaning it can't be added dynamically through other code, but first-child is a CSS2 selector, whereas last-child was added in the CSS3 specification)

Note: This only works the way you intended if you only have 2 items in the list like your example. Any 3rd item and on will have borders applied to them.

The :last-child pseudoclass still cannot be reliably used across browsers. In particular, Internet Explorer versions < 9, and Safari < 3.2 definitely don't support it, although Internet Explorer 7 and Safari 3.2 do support :first-child, curiously.

Your best bet is to explicitly add a last-child (or similar) class to that item, and apply li.last-child instead.