monoblue: visually highlight source lines when hovering over line numbers Due to how the line links now reside outside of the source lines, hovering over line numbers doesn't count as hovering over the appropriate source line. It can be worked around by using a "+" css selector. However, it's necessary to reorder the elements and put <a> before <span> (which is actually quite logical). It works without further css tweaks because <a> is already absolute-positioned and so the order doesn't matter visually.