My 1998 honda accord will not start when it is really hot outside,but it will when its cool outside can anybody tell me why?

You need to replace the Main Relay--it's an extremely common problem with Hondas in hot weather. You want to remove the fuse box cover and the lower dash cover. It should be located under the dash, just to the left of the steering column. Turning the ignition key on and off will help you locate it, by hearing and feeling it click.