whats this error about ??

[PHPycho]

Hello forums!!
I tried to insert following query in the table called user_table

INSERT INTO user_table (id,username,realname,email,password,date_created) 
VALUES
('','user1','user name','user1@localhost','1a1dc91c907325c69271ddf0c944bc72',now())

I got the following errors(in Phpmyadmin):
Error

SQL query:

INSERT INTO mantis_user_table( id, username, realname, email,
PASSWORD , date_created )
VALUES (
'', 'user1', 'user 111', 'rajen@localhost1', '1a1dc91c907325c69271ddf0c944bc72', now( )
)

MySQL said: Documentation
#1062 - Duplicate entry '' for key 2

My table structure is:
[syntax="sql"]CREATE TABLE user_table (
id int(10) unsigned NOT NULL auto_increment,
username varchar(32) collate latin1_general_ci NOT NULL default '',
realname varchar(64) collate latin1_general_ci NOT NULL default '',
email varchar(64) collate latin1_general_ci NOT NULL default '',
password varchar(32) collate latin1_general_ci NOT NULL default '',
date_created datetime NOT NULL default '1970-01-01 00:00:01',

PRIMARY KEY (id),
UNIQUE KEY idx_user_cookie_string (cookie_string),
UNIQUE KEY idx_user_username (username),
KEY idx_enable (enabled),
KEY idx_access (access_level)
);[/syntax]

I am unable to figure out the problems
Please help!!
Thanks in advance to all of you.

[bradgrafelman]

When inserting rows in SQL, if there is a column specified as AUTO_INCREMENT, you should not list it in the INSERT query. MySQL will handle this column's value by itself; specifying it in the column list of an INSERT query will attempt to force a value into that column which, as you're experience, often causes errors.