A common mistake is to assume that these two words can be used interchangeably. By definition, 'accuracy' is the degree of veracity, while 'precision' is the degree of reproducibility. Whatever the hell that means...
What's the point, you ask? I'm not too sure if there's a point to this, but let's see if I can create one along the way :)
Now, I'm going to attempt to explain the difference between accuracy and precision, using a target comparison as analogy. Read and learn! (if there's anything worth learning from it, that is). In this analogy, repeated measurements are compared to arrows that are fired at a target:

Accuracy describes the closeness of arrows to the bullseye at the target center. Arrows that strike closer to the bullseye are considered more accurate. The closer a system's measurements to the accepted value, the more accurate the system is considered to be.

To continue the analogy, if a large number of arrows are fired, precision would be the size of the arrow cluster. (When only one arrow is fired, precision is the size of the cluster one would expect if this was repeated many times under the same conditions.) When all arrows are grouped tightly together, the cluster is considered precise since they all struck close to the same spot, if not necessarily near the bullseye. The measurements are precise, though not necessarily accurate.
Are you with me, so far? *sigh* just keep reading will you...
However, it is not possible to reliably achieve accuracy in individual measurements without precision - if the arrows are not grouped close to one another, they cannot all be close to the bullseye. (Their average position might be an accurate estimation of the bullseye, but the individual arrows are inaccurate).
A mate attempts to describe my character, which I think is superb example of precision, but not necessarily accurate. Obviously, I know myself best...
DipSteR says:many ppl r just plain transparent & highly predictable, like meGupioli Di Bajajio says:i dont think u areGupioli Di Bajajio says:i think ur a specimenGupioli Di Bajajio says:ur very politically correctDipSteR says:yeah riteGupioli Di Bajajio says:
u never tell ppl wats truly goes thru ur mind
Gupioli Di Bajajio says:
ur a hard nut to crack
Err, you get the point? If you think you just read a load of crap, think again.