Comment by romdev

This works on HN and most other sites:

javascript:(function() { var tag = document.createElement('style'); tag.type = 'text/css'; document.getElementsByTagName('head')[0].appendChild(tag); tag[ (typeof document.body.style.WebkitAppearance=='string') ? 'innerText' : 'innerHTML'] = '* { background-color: white !important; color: #444 !important; } html { filter: invert(100%) grayscale(100%); }'; })();