Hi - I am knew to javascript and trying to work on a new website. I am trying to create a rollover gallery (Thumbnails and large pic in the center. When mouseover a thumbnail, image appears in large image in center)

Anyway, I did research online and thought I had the answer - didnt work. Could someone give me the exact script/codes to use to do this? Can you use jpg or does it have to be gif?? PLEASE HELP!!