cleaning out template1, and what is template0?

It sometimes happens that template1 gets accidentally littered with
tables and sequences intended for other databases (forget to \connect,
wrong arg to psql, etc.).

Is it safe to DROP/CREATE template1 for a radical cleanout or should I
merely remove cruft by the item?

In Pg-7.1 there is a new template0 db. What is it used for?

Thanks in advance,

--
THESEE: Quel coup me l'a ravi ? Quelle foudre soudaine ?
THERAMENE: A peine nous sortions des portes de Trzne,
Il tait sur son char. Ses gardes affligs
Imitaient son silence, autour de lui rangs ;
(Phdre, J-B Racine, acte 5, scne 6)