Removed extraneous presentation properties from %accessible-invisible-show.
Reduced extraneous presentation CSS for the skip link functionality down to the class .wb-skip-link which should be applied directly to each skip link instead of a container and only toggles the display of the skip links on focus.
Updated the layout templates to use the new skip-link CSS.
Moved the presentation CSS properties for the skip links to the theme.
Eliminated the use of important in the accessible-invisible CSS.
Removed duplication of presentation CSS for :link and :visited for the skip link CSS.
Merge pull request #3042 from thomasgohard/skip-links

Changes to skip link CSS