Due to the special border-rounding rules, a "border-width:1px" does not necessarily have the same layout effects as "border-width:3px; margin:-2px;". (On my screen, the latter was 1 device pixel smaller, causing jiggle as I hovered.) Instead, just use a consistent border+margin all the time.
Also:
removed the text-decoration properties (text-decoration was explicitly turned off so these did nothing)
Due to the special border-rounding rules, a "border-width:1px" does not necessarily have the same layout effects as "border-width:3px; margin:-2px;". (On my screen, the latter was 1 device pixel smaller, causing jiggle as I hovered.) Instead, just use a consistent border+margin all the time.
Also: