When you've created a project--such as a website--that you know that you'll be needing later as a basis for a new project, Flash has a convenient option that lets you save the project as a template to be loaded from Flash later. True, you could always just open the original project and save a copy of it to work from, but if you're anything like me you've probably got dozens of Flash files saved in a disorganized mess across multiple hard drives--and finding the right version of the file you need weeks or even months later may be downright impossible. Saving the file as a template from the start will save you the time and headache of hunting it down again later.
To save a file as a template, make sure that the version of the file that you want to save is open, and then select File->Save as Template.