It's very useful read webpages with White text and Black background.
So I suggest this two addon for Firefox and Chorme that give you the ability to don't tyre your eye:
Blank Your Monitor + Easy Reading 1.9.8
High Contrast
Per evitare di affaticare gli occhi ho trovato due plugin per firefox e Chrome che rendono il testo bianco e lo sfondo nero.
Blank Your Monitor + Easy Reading 1.9.8
High Contrast
