Black HTML background

I find it straining to read web pages with large amounts of light text on black backgrounds. After looking at such pages for a prolonged period of time I would experience burnt-in effects in my eyes similar to that of a computer screen. I then have to squint my eyes in order to recover, just like activating screen savers. It's kind of funny as my initial personal web pages employed such white-on-black design themes. It's not until someone told me the problem that I started to experience it myself.