session and frames

Hi, I am trying to use session variables to ensure that the user has logged in before I display the pages in frames so I do session_start() in the page that holds the frames and I register the username but it gives me "headers already sent" error when I do a session_start() in other pages to check if the username variable is registered. Can anybody help? -- Mathieu Dubé mat@syspark.com Programmeur-Analyste mat.dube@videotron.ca Syspark Inc.