Can't execute query

SELECT message FROM tblMessages messages
				WHERE siteid =  AND enable = 1 AND messagetypeid = 2
				ORDER BY messages.lastmodified DESC LIMIT 3

MySQL Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AND enable = 1 AND messagetypeid = 2 ORDER BY messages.lastmodified DESC LIM' at line 2

This script cannot continue, terminating.