Led Zeppelin is not Satanic, Jimmy Page had an interest in the occult, which led to the band being branded as Satanic, however, there was no Lucifer worshipping going down.
No. The Beatles weren't interested at all, and Zeppelin's Jimmy Page was the only member to be interested in Satanism; however, he's never been a Satanist.
Many people claim that if you play their songs backward (Stairway to Heaven, in particular) that you'll hear satanic messages, but there is no real evidence that they practiced any form of Satanism.
Because when one of the verses is played backwards, it sounds like it is saying So heres to my Sweet Satan. The one whos little path Would make me sad, Whose power is satan. Hell give you 666. there...