Oh, this puzzle.
To prevent you from answering it, I have a muzzle.
Relax on that sofa, and nuzzle.
The answer to this puzzle, is subtle.
It shall make your brain shuttle.
From Point A to Point B, you will scuttle.
The key is the margin.
Like a wall, that you barge in.
Oh, that doesn't make sense.
Let me help you, turn J into I, and commence!
Before I forget, the funny slang is the key word, isn't that just common sense? And ignore this line's margin!
Using the above poem, decrypt the phrase below
ETLN DI GIHILKF ILFANON, cpek'b ocf?