About optimizing - Adobe Fireworks

Optimizing graphics in Fireworks involves doing the following:

Choosing the best file format. Each file format has a different method of compressing color information. Choosing the appropriate format for certain types of graphics can greatly reduce file size.
Setting format-specific options. Each graphic file format has a unique set of options. You can use options such as color depth to reduce file size. Some graphic formats such as GIF and JPEG also have options for controlling image compression.
Adjusting the colors in the graphic (for 8-bit file formats only). You can limit colors by confining the image to a specific set of colors called a color palette. Then you trim unused colors from the color palette. Fewer colors in the palette means fewer colors in the image, which results in a smaller file size for paletted image file types.

You should experiment with all optimization controls to find the best balance of quality and size.