What exactly is an "uncorrectable sector"?

I was using the SMART detecting program and it told me I had 1 uncorrectable sector. I ran a checkdisk today but I didn't see the results as it finished before I got back and I can't find the logs on Vista :-o (if someone could please tell me where it is, it'd be appreciated.) Is it something to worry about?

EDIT: Found the checkdisk after some googling and searching.

Also, what the heck is going on with that TTF file? :-D

 

Thanks. So it's nothing to worry about unless a bunch of them suddenly pop up, correct?

 

That is the group of files (if you look closely they have different endings) that were stored in the bad sector, and were recovered to an undamaged sector.

 

if you have had a uncorrectable sector on your drive that means your hd will start crashing soon i have had this problem my self.best idea would be too start saveing your info on that to a disk or a flash drive stick.