Stop what you're doing. Download and install this program on your computer right now: f.lux (for Windows, Mac and Linux)
Your computer monitor is designed to behave like the sun - blasting out a full array of bright colours. That's fine during the day, but at night, computer monitors can look WAY too bright and blue, which strains your eyes (or worse, gives you headaches and sleep issues!).
Flux reduces eye strain during evening computing sessions by matching the colours on your computer monitor to the lighting conditions in your room and the position of the sun. You install the software, tell it what type of lights you have in your primary computing location (incandescent/florescent), and tell it your geographic location. DONE. Flux does the rest, "warming up" the colours of your monitor in the evening.
At first, you might find this software incredibly annoying. You may be tempted to think "my computer practically looks orange at night". I urge you to try this software for at least two weeks if you use your computer regularly in the evenings, or a month if you're an occasional nighttime user. I hated Flux at first but now can't compute at night without it. Over time you get used to the software adjusting your on-screen colours automatically, and you even come to depend on it for sanity. I accidentally messed up my settings a few weeks ago, and dropped everything I was doing until I fixed it. I just can't compute on a brain-scorching bright blue display at night!
I absolutely recommend this nuisance-free, hassle-free software to everyone out there.