If this is the first time you've noticed this, and it's more than a couple spots, I would get your doctor to check it out. The first time it happened to me I freaked out!
Bright red likely means a hemorrhoid or a scratch is bleeding. Dark and tarry could be much more serious. Either way, your doctor can let you know how to deal with it, or how to help things move more smoothly in general.
I get bad constipation and end up with some bleeding fairly often. If it's bright, stops quickly, and doesn't look like too much, then I don't worry about it.