What a waste

Why does my eye drag me to signs that are to all intents and purposes normal signs, but on closer inspection are such grammatical failures of instructions?
This sign in the Cornhill area of the city has been there for years, but I just noticed recently that the only thing the council want you to throw away in the adjacent wheelie bin, are the local residents.
Also if you do leave refuse here, the residents are not allowed to have it.
To see a previous photographed sign go here. This one is in the grounds of the local college that teaches woodwork etc. It used to called The Technical College. Most definitely a fail.
A note on the song link, on the cover of Ian Dury's New Boots and Panties album, alongside the man himself, is a small boy. Well that boy is Ian's son, who has a record out himself now. I heard it on 6music a few weeks ago, and I have forgotten already what it sound like.