Absurdity

You are walking through a forest and all of a sudden you come upon a magic Green Glass Door. You walk around the door, trying to find a way through, but you can't figure out how to get through the door. As you continue your investigations you find only certain objects can go through. Can you figure out what can and can not go through the Green Glass Door, can you figure out the magic behind the door (there is a way to win)?

• Trees can go through the green glass door, but no branches.
• There is a hell beyond the green glass door, but no heaven.
• There is Google and Yahoo on the other side of the green glass door, but no Microsoft.
• There are tomorrows, but no yesterdays.