Reworked yearly archives  and new link colours

Reworked yearly archive links to the preceding archive to ensure the
link always points to a valid archive – this protects against empty
pages if a blogger skips posting for a year.

Added pink text colour for hovered/focussed links (cherry blossom pink
in keeping with the theme’s name =)

Posts in the yearly archives now highlight with multiplied pink when
hovered/focused.

Fixed silly CSS problem in error.php.