Thanks for enlightening me, Chris; I didn't know anything whatsoever about Twitter, with the exception that a tweet can't be more than 140 characters.
I once thought of having a peep at the site to see what it was all about, but you have to sign up for it even to do that (unlike Eratosphere). Needless to say, I shan't be bothering!
Once again, well done to all of you who won this comp despite not being Twitters yourselves
Jayne