What is the story behind the Beatles CD cover "Abbey Road"?

I was on my way home from work the other night and I just caught the last bit on the radio about this theory behind abbey rd. I like the Beatles but I'm not one of their biggest fans. The guy on the radio was saying that Paul McCartney had really died in a car crash and because they were so big at the time they had to hide this at the time. There is 9 or more points (clues )on this cover seemingly. My Question is can anyone tell me the story behind the Abbey rd CD theory cover .Id just like to know now because ever since I heard it its like one of those stories that really you just have to know.