We may be mistaken about the facts; we may think something true that is not actually true. This is an issue of epistemology; this is not an issue with truth itself. Besides, people can only be mistaken about the facts if there is some truth about which they are mistaken. Like I said before, in my 'textbook answer':
Originally Posted by Nicodemus
True propositions exist independent of our beliefs about which propositions are true. We may be right or we may be wrong. Whether a proposition is true and whether we know it to be true are separate issues; the absence of certainty or knowledge does not entail the absence of truth.
The statement 'Jupiter is larger than the Earth' is true if and only if Jupiter is actually larger than the Earth. When we think a proposition is true, then we think it describes the facts, because that's just what it means for it to be true. Might we be mistaken? Of course, and we spend a great deal of time and resources testing for such errors.