When designing a website, designers have many choices between various applications.
Should they use Adobe Photoshop or other software? Well that’s clear that Adobe Fireworks cannot compete with Photoshop and it is not it’s purpose. It was designed as a powerful web layout and graphics software and it is good at it. Fireworks is mainly / primarily a vector application, but it offers bitmap editing features that web designers need. This vector-raster editing capability makes it the industry leader for prototyping and rapid web-site building.
You can read more about Adobe Fireworks on Smashing Magazine.