Script Summary: Improves readability by blackening grey text that's #666666 or darker. I wrote this to counteract the now-popular fad of making body text grey -- which decreases contrast unnecessarily.
Most of my friends claim not to notice or mind that a lot of body text out there is grey. I notice and mind, and I thus wrote individual scripts for sites I visited often that used such text. It later occurred to me to just make a set-it-and-forget-it script that would apply to all sites and only blacken text that's already pretty close to black already. Here it is.