Buttons are created like any symbol. You have two options:
When you first create a Button Symbol, you will notice the biggest difference between it and the Graphic Symbol is the timeline. Button Symbols have timelines, but they are different in that rather than playing from the beginning to end, they have four special frames: Up, Over, Down and Hit.
These frames allow you to specify what changes will take place as the mouse interacts with the button. This file is saved as Buttons/demos/Buttons.fla.
Just like any other timeline, you may only edit keyframes. Add keyframes or blank keyframes just as you would normally. Any change that occurs between the up and down states will appear to the user when the mouse rolls over the button. Down is what appears when the mouse is pressed down.
The hit state is used to designate the trigger area. If you do not specify an area, all the visible content will serve as the trigger area. You need not use the hit frame unless you want to specify an alternate area for the trigger area. The hit state is great to use when dealing with irregular shapes that involve transparency.
As you will see below, the Hit state is commonly used with a text button.