Everyone prolly knows of the scandal involving reverse lyrics in Stariway to heaven. If you haven't look below:
1. Stairway to heaven. Listen to the song (in AAC format) Here
2. Lyrics to the complete song are here: Here
3. Here are some cool sites dealing with this:Here
Look at this though. They say Here
that Backwards speech comes basically as natural as forward speech, but it's imply dont at a subconscious level.
So essentially, it could be that zeppelin didnt put it in the song intentionally... Its kinda confusing.