I believe it means the same as redline. It would seem the older generation referred to the comparing of two documents, one being the original and the second, the revised, as "Redlining". The younger generation refers to it as "Blacklining".
Blackline GPS was created in 2004.
A blackline tilefish is a species of tilefish, Latin name Caulolatilus cyanops.
A blackline is a document indicating the differences between two versions of another document.
A blackline version of a document is the final version after all revisions have been accepted.
Blackline The Beirut Contract - 2014 was released on: USA: 2014
what does an email ending '.me' mean?
What does a 3 at end of email mean
email corriente
Subject Is What The Email Is About.
Its mean its for password and email so you can login.
it means use a backup email
It means constantly check email