Linux question

I run Ubuntu 2.6 and every now and then i get this thing that comes up when the computer boots that says:

"/ has not been mounted in 30 days, check forced "

then it starts loading something...

What does this mean?

its nothing to worry about, just doing a routine check of the disk for errors. The frequency can be edited in the fstab:
sudo gedit /etc/fstab
(if you think you know what you're doing, make a backup etc. )

Yeah usually its either a time or number of mounts, whichever comes first that will cause the system to check the disk. It isn't any big deal.