This is a bug called the floating jukebox bug that I encountered in snapshot 13w19a. A summary of this issue is in the description.

Well I was on one of my world's and was using creative mode on it. Well I was in a building that I built and the building had clay floors. Well I put a carpet on one of the clay blocks and then I placed a jukebox on the clay block that I placed the carpet on. Well instead of the jukeboxes being on the ground they were floating. This bug annoys me now and I hope it's fixed soon.

What I expected to happen was...:
I thought that everything would go like normal and I didn't expect to encounter this bug either

What actually happened was...:
I already described what happened in the description.

Steps to Reproduce:
1. Dig a hole one block deep.
2. Fill in the hole with any block.
3. Place a carpet on the block that you used to fill in the hole.
4. Now place a jukebox on the block that you used to fill in the hole and now you have a jukebox that's in the air when it's supposed on the ground.