If you use MYSQL 5 just change the first comma before the the left join into inner join !
select p.products_id, pd.products_name, p.products_image2, p.products_price, p.products_tax_class_id, if(s.status, s.specials_new_products_price, NULL) as specials_price from products p INNER JOIN products_description pd left join specials s on p.products_id = s.products_id where pd.products_id = p.products_id and p.products_id in(99, 100, 101, 102) and pd.language_id=2