Just follow these Guidelines
STEP 1 : Login to your facebook account
STEP 2 : Open the chat box of the person for who you want to get offline
STEP 3 : On the upper right corner of chat box there is a icon like settings click on it
STEP 4 : Now from the drop down menu click Turn off chat for……
done…..!!!!!!!! now you are visible offline for that person
To get online for him Repeat STEP 1,2,3 and then click Turn on chat for…