I love the easy questions. To tell if an egg is bad, follow these steps:

1. Get out a bowl or pot and fill it with water. You need 4-6 inches of water, but you do not need much width in the pan. You're not cooking the egg.
2. Gently put the egg in the water and release it. If the egg sinks, it is good. If it floats to the top, it's bad.

If it kind of "hovers" in the water, neither sinking nor floating, it's still OK, but it's on its way out. Don't undercook it or eat it raw, and use it up soon.