I assume you use redhat. next time when you ask technic questions, indicate your OS, version, and any background that relates to your problem.
if the disk is formatted previously under windows, you need to do this:
$>mount -t vfat /dev/fd0 /mnt/floppy
if the disk is unformated you can do this:
$> mkfs -t vfat /dev/fd0 1440 && mount -t vfat /dev/fd0 /mnt/floppy