Ranna, I don't know about PostgreSQL, but in Oracle you don't need to say when a column *can* be null, only when it can't. So...

CREATE TABLE users
( uid     INTEGER(4)    PRIMARY KEY,
username  VARCHAR(15)   NOT NULL UNIQUE,
passwd    VARCHAR(10)   NOT NULL,
realname  VARCHAR(50)   ,
email     VARCHAR(50)   NOT NULL UNIQUE,
website   VARCHAR(50)   ,
face      VARCHAR(20)   ,
bio       VARCHAR(75)   );
[download]

(but as I say, I haven't used PostgreSQL)

Also, it might be worth thinking about dropping the uid column - if both username and email are unique, then you could use either of them as the primary key.

You might well find this book interesting too.

good luck - andy.