Requesting data of 2 tables
Try this query, I've reformatted it to make it easier to read.  You really should specify the type of join (INNER, LEFT OUTER, etc.) and specify how they are related.  

SELECT a.title
    ,a.discription
    ,a.supportername
    ,a.reportername
    ,a.member_id
FROM ticketdata a
    INNER JOIN marked b ON b.ticketid = a.ticketid 
    INNER JOIN users u on u.member_id = a.member_id
WHERE u.id = ".mysql_real_escape_string($_SESSION['id'])."
    AND b.active = '1'