In this presentacion we can see how comet's antitails envolves and change in usual tails of a comet:
The nucleus of Comet Lulin spews a mixture of dust and gas into space. Quickly, the mixture separates into two distinct tails: The gaseous "ion tail" is pushed straight away from the sun by solar wind. The weightier dust tail resists solar wind pressure and aligns itself more or less with the comet's orbit.
The next image shows why the ion tail disappeared: It is temporarily hidden behind the comet's head
And finally we see prediction for the future: The ion tail will re-appear during the early days of March. The two tails, ion and dust, and sometimes called the tail and the antitail.
Thanks to spaceweather for the cool link and text ;)