What was that addon that stops my Facebook friend from seeing whether I have read his/her message or not?

ReĆ½ Aetar September 13, 2012
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Few days ago I read about an addon that prevents my friend from seeing whether I read his message or not on Facebook. What is that addon called?
Please, need help fast! Thank you!

  1. Hama Charieg
    September 13, 2012 at 2:04 pm
  2. susendeep dutta
    September 13, 2012 at 7:43 am