Fireworks has the unique ability to allow users to define some “universal” or “master” elements(Page) for the entire site (like navigation and branding)
As Adobe help guide Says :
If you have some elements that you want to be common across all of your pages, you can use a master page.
When you convert an ordinary page to a master page it moves to the top of the list in the Pages panel and it is colored gray.
When a master page is created, a Master Page Layer is added at the bottom of the layer hierarchy for each page. This layer can be removed by selecting Remove Master Page Layer from the Options menu in the Layers panel.
The visibility of the master page layer can be toggled by clicking on the eye icon to the left of the master page layer in the Layers panel. If you change the master visibility on one page, this change is reflected across all of the pages. For more information about controlling the visibility of layers see Protecting layers and objects.
To create a master page
• In the Pages panel, select a page that you have already created and choose Set As Master Page from the Options menu.
A Master Page cannot have shared layers, so when you make a page into a Master Page, any shared layers are removed from it and changed to ordinary (non-shared) layers.
To link pages to the master page
After a master page is created, any additional pages that are created inherit the master page settings such as canvas color and size. Pages that already exist do not inherit these settings unless they are "linked" to the master page. In addition, if the master page settings are later changed, none of the other pages will inherit these changes unless they are linked to the master page.
Do one of the following to permanently link a page to the master page:
• Select the page in the Pages panel and choose Link to Master Page from the Options menu.
• Click in the column to the left of the page thumbnail in the Pages panel. A link icon displays to show that the page is linked to the master page.
if you later want to add the master page layers back into the page, select Add Master Page Layer from the Layers panel Options menu.
To change a master page back into a normal page
• Select the master page in the Pages panel, and then choose Reset Master Page from the Options menu.
Give a read to this Fireworks Layers
Hope this thing helps you a bit.....