The group responsible for the standards that various TV Shows and other videos use have released new information on updates they have made to the old XviD standard for TV Shows.
These changes went into effect as of 2012-02-22 16:00 UTC.

The change is as follows: the older SD Xvid .avi standard has been replaced with a new SD x264 .mp4 standard. What this means is that as of the current writing of this news post our FAQ/rules are out of date. The .mp4 standard is going to be allowed in the normal category for the TV Show it belongs too and the FAQ/Rules will re-written/updated over the next few days.

For Example:

The old release group rules would have made the file name:
TVSHOW.S01E01.HDTV.XviD-RLG.avi

The new release group rules now make the file name:
TVSHOW.S01E01.HDTV.x264-RLG.mp4