If you need to support older browsers (IE7+, etc...) you should flip the border from the right side to the left side, so that you can use the css selector first-child.
Change your current css from this:
#navigation li a { color: #ffffff; line-height: 22px; font-size: 11px; text-decoration: none; padding: 5px 15px 6px 15px; border-right: 1px solid #ffffff; } To:
#navigation li a { color: #ffffff; line-height: 22px; font-size: 11px; text-decoration: none; padding: 5px 15px 6px 15px; border-left: 1px solid #ffffff; } #navigation li:first-child a { border-left: none; }