Fairy optic motorcycle

What are these things I keep seeing in people's lawns [Picture]? - white shepherd hooks

I still see these strange things on the lawn of the people. It is a square of yellow plastic with a white plastic bag hanging from her green notes. I think the green color are marked words. In addition, the bag is always shining in the middle of twisted. The entire apparatus is usually exposed to the hook of a shepherd. I drew a portrait and uploaded a to Flickr. I am now so confused, it's winter and everyone is in the garbage, and I know that no one knows what they are, and even less for ads. But seriously, it is literally in all three houses in my town.

Based on Flickr: http://www.flickr.com/photos/29108357 @ N0 ...