SELECT competition FROM table_name_75 WHERE notes = "400 m hurdles" AND year < 2004 AND venue = "johannesburg, south africa"
Sebelum 2004, apa nama kompetisi yang terjadi di Johannesburg, Afrika Selatan dan memiliki acara rintangan 400 m?
CREATE TABLE table_name_75 (competition VARCHAR, venue VARCHAR, notes VARCHAR, year VARCHAR)