Adobe Fireworks is best product for web design, better than Photoshop for many specific features.
Many designers use Photoshop for website design. This software is certainly an amazing way to create and manipulate images. But, in my opinion, it is not the best way to web design.
Create a web layout is a complex job mixing texts, images, textures and graphical objects. For this reason Photoshop is not the best useful tool.
Instead Fireworks does all of this because it is not only a bitmap software, but has excelent vector and web oriented functions too.
Important feature of Fireworks is pages management. In Photoshop, and in other bitmap manipulation software, you can work in single canvas only. One file, one image. This is correct if you need image editing, or single artwork creation. But in projects with many pages like website this is a limit. So, if you must create a brochure you can do it with Photoshop, but probably you will use Illustrator. For same reasons, for websites you can use Fireworks, that allows to create many pages in single file and also to share elements between pages.
Another useful feature is possibility to create links between pages. In this way it is easy to export demo of your creations, in html or pdf.
10 Reasons Why I Prefer Fireworks CS4 To Photoshop For Web Design
Eight designers are choosing their favourite tool: Photoshop vs Fireworks, on Digital Web
Design a Website with Fireworks
On Adobe Tv a great selection of other video tutorial for Fireworks