curl is showing 200 ok but pool member is down .

Hi Team , 1)i am able to do the curl from my F5 to member i am getting 200 ok page and able to ping as well . even though my pool member is showing down . what are all the possible cases 2) Can we configure multiple strings (like "200 ok" or "server up" or "i am good" )in server side for probing F5 and same way is it possible in F5 receive string .