Kernel panic not Syncing:VFS:Unable to mount Root fs on unknow-block(0,0)

Kernel panic not Syncing:VFS:Unable to mount Root fs on unknow-block(0,0)

This is happening on USB version 13.04, too many times. I have tried the
suggestions but I am not able to proceed to get the commands to be
accepted when I type in. Can someone be more precise in the instructions.
I type in this ok: sudo mount /dev/sda1 /mnt But this line it gives error:
mnt/dev does not exist??? sudo mount --bind /dev /mnt/dev