My eyes used to feel very tired after spending a few minutes at the PF, to the point where I had to stop visiting the PF pages. I didn't (and don't) know why that happened with the PF and not with other websites. Then, I switched to LCD monitors. At the same time, put them much closer to the keyboard (less distance between eyes & monitor). Now the strain is almost entirely gone. If anyone is reading this with strained, red, dry (alternatively, tearful) eyes, consider making these changes -- what worked for me might also work for you.