Error dropping non-existent tables

Hi,

I am a new PostgreSQL user and am not sure if this is the correct list
for this question, please redirect me to the correct list, if needed?

I recently starting using PostgreSQL 8.0.0-beta4 (Win32) and want to
migrate some of the SQL scripts written for MySQL to PostgreSQL. I
have the following SQL command, is there an equivalent version for
PostgreSQL?

"DROP TABLE IF EXISTS my_table CASCADE;"

I am able to drop tables in PostgreSQL, but the problem arises when
the table does not exist and I try to execute a "drop table" command.

thanks in advance,
Baldeep.