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Don't panic -- this is a very recoverable situation. You can save to the floppy disk from the terminal. First get a DOS formatted floppy and insert it into your machine, then you must mount the disk -- the command generally looks like 'mount /dev/fd0 /mnt/floppy' (no quotes, and you may need to create the /mnt/floppy directory first). The copy files to /mnt/floppy as normal, 'umount /mnt/floppy' when done, and eject the disk.
Also, you can edit your /etc/profile from failsafe mode (probably signle user mode -- not sure how Fedora does it). The pico editor is probably the easiest to use from the command line. In the future, when making profile changes for yourself, you should make them to your own custom shell startup scripts in your home directory, so there's no chance of screwing up the system wide startup scripts. The more I think about it though, the more likely I think it is that you did something else wrong, since editing /etc/profile shouldn't by itself stop the GUI from starting up correctly. Have you done anything else to the machine?
Oh, and for future reference, it helps if you post a more descriptive title specifying your problem.