Apparently the electrons build up on the inside of the screen with time, and the picture deteriorates. I found a free program that I used to 'clean' the inside of the screen and the improvement was quite noticeable. I highly recommend it. If you'd like to try it, simply click on the following link.
The program is free, works automatically, and takes only about 45 seconds to do its job.
Screen Cleaner
Make sure the sound it turned up
