In MineCraft 1.4.6 In A Server Or Single Player If You Place 2 Blocks that Fall, Sand, Gravel, Anvil On Top Of Web It will Bug Out And Be 2 blocks At Once

What I expected to happen was...:
Block Would stay On Top Of The Web.

What actually happened was...:
The Block Was In The Other Block
In The Web Falling

Steps to Reproduce:
1. Make A Piller Of Blocks 1x1
2. Place web At the Bottom
3. Place A Fallable Block (sand, Gravel, Anvil) 1 Block Above