I would like to know more about Active Area and creating a slice in FW. Why we need it and how we use it in a workflow.
Also about setting it. Is it set all by itself when we create a button or we have to open Active Area item of a drop down menu in symbol properties window?
An Active Area is the area of a metallic rectifier that acts as the rectifying junction and conducts current in the forward direction. Just kidding. :-) It's the area of a web page that responds to the viewer's cursor, generated automatically when you create a button and add states to it. You can do that via the properties panel, by double clicking on the button symbol to activate Fireworks symbol editing mode.