How to disable seen option in facebook chat ?

Facebook recently updated a new facility which is the "seen" option in the facebook chat box .

When you are chatting with your friends on facebook , and when your friend reads your message , it displays "seen" along with the time when your message was read . Actually it is a very good feature , but sometimes it lets your friends know that you are ignoring their messages .

In the past you can just skip the chat by not giving reply to your friend , but now when you have read the message it shows as "seen" , Many of my friends asked me how to disable the "seen" option in facebook chat ? But now it is possible by adding an extension or add-on in your browser .

For Google Chrome Users - 

1) Just install facebook unseen .

When you have installed this Extension it will get enabled and enjoy .

For Mozilla Firefox Users -

1st Method :-

1)Just install GreaseMonkey .

2)Then install facebook stealth .

All you have done now enjoy .

You can also install Chat Undetected for Google Chrome , Mozilla Firefox and Internet Explorer .