I created a new account using the grant command as follows:
GRANT SELECT, UPDATE, INSERT ON mydb.* TO 'johnny'@'%' identified by 'johnnypass';

I have two problems:
When I try to connect to the server using:

mysql_connect('localhost', 'johnny', 'johnnypass')
I get the following error:
Access denied for user: 'johnny'@'localhost' (Using password: YES)

how I provide this new account with privileges to access the server?

I also tried to revoke this account and remove any traces of it using:
REVOKE ALL PRIVILEGES FROM 'johnny@localhost';
I got the following error:
You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM 'johnny@localhost'' at line 1

Is this all I need in order to remove the account? do I need to also drop the user?