regarding oid(object id)

Hi
i am novice postgr sql user.

I have created a table named customer in my data base.
also i have inserter some of the rows into my table.
when i try to execute this command to select object id's (oid) i am getting
following error.

select oid from customer;
error: column oid doesn't exist

note: even though i have changed the
default_with_oids = on in postgreconf file,i am not getting the oid's.

my postgre sql version is 8.4

but when i try to select oid's for already existed tables in pg_catalogue
the output is coming
for eg: select oid from pg_proc;

please reply

thanks & regards
sivakiran.B