Imporent Quesion

I had a ccount on dream host company and i added another domain to now i get two accounts in to my FTP. Now the proplem is As soon as you guys added my new account to the old one i get this proplem which is i alwayes have to add index.html Or index.php to the link i am going for so i can reach it it dont work with out adding index.html Or htm Or php any help please ???