In addition to Boomerang's post, I'd like to tell that those special code entities are good only for IE. Other browsers behave differently: Opera just ignores them and shows title text in one line, Mozilla does the same but adds some other chars (that sometimes look as rubbish). So be careful.
Also, if you just want to write some text on several lines (without any other formatting), no any code entities needed, just press [Enter] in your code editor:
title="this comment press [Enter] here
will be shown on several lines. press [Enter] here
(IE-only, others display it as one line)"
Also, I forgot to add that TITLE attribute is not supported by NN4 - it is just ignored there.