I'm new, and tried to 'contribute' a tab of chords for a song I notated, but it's status now says 'D' which I presume means declined... why? Because I have no idea...
The users of U-G are allowed to vote on newly submitted tabs. If there are already several versions of a submitted tab and you submit another, it will probably be rejected. If you submit a tab and it has too many errors, it will likely be rejected. There are several reasons why it wasn't accepted.

As already mentioned, this is quality control.
Thanks... I just realised I had an email explaining this *facepalm* I should check first next time and it was a song not already on the site... but not a well known song