I'm a little confused by why I can't place a bed on a floor of glass in 1.7.2. I can place other objects, such as furnaces and crafting tables, without difficulty. However, my bed refuses to be placed. How can I get around this and why is it happening?
From the Minecraft Wiki:
Like certain other blocks, beds can not be placed on snow, ice, glowstone, glass, carpet or leaves. If you remove the blocks underneath the bed, the bed will not be removed, but will remain floating. To put a bed on glass you must use this trick to make the bed float, and after that place the glass underneath.
For an alternative explanation, see this video.