Never heard of that before. Says its used in the UK, and minichan has nothing to do with the UK.
@previous (r04r)
Half of what I say if bollocks. You can ignore that half.
@previous (A)
It seems unlikely they would be published online, feels like it would somewhat defeat the point. That said, I had never heard of them before, so not a clue.
I've never heard of a D-notice being issued to a non-print publication of any kind. They're advisory notices; basically 'Please don't talk about $x or some aspect of $x". They're requests made to newspaper editors, usually, and they're not made public unless either Parliament (or the Government) or the recipient chooses to.
I'd be more concerned with NSLs on US sites & services, if I were you.
(Edited 58 seconds later.)