Sources of error for titration experiment.

I have to write a table for the sources of error for a titration of salt and rock water against silver nitrate. any ideas apart from the subjective judgment of the colour changing?

i realise titrations are a chemistry experiment but it was in biology so i thought i would post it here.

Errm you'll have the calibration of the equipment used (burette/pipette) etc which will have a accuracy range (I've totally forgotten what it's called, but it's the thing where it's like....2.5ml +/- 0.001ml for example if you get what I mean)

And my brain has totally mushed as I can't think of anything else

Google......is a wonderful thing
http://www.titrations.info/titration-errors

yes! i went downstaires and thought of this myself. all the quantifiable errors could be put in.

Errm got another one, not sure if it's any good, but you could have some of the water evaporating maybe?

Errm you'll have the calibration of the equipment used (burette/pipette) etc which will have a accuracy range (I've totally forgotten what it's called, but it's the thing where it's like....2.5ml +/- 0.001ml for example if you get what I mean)

And my brain has totally mushed as I can't think of anything else