If you have used transparency in Fireworks, the transparency pull-down menu may already be set to Alpha Channel or Index. The color you have selected will turn into a checkerbox pattern in the view window. The last box is for interlacing, which is similar to the progressive option for .jpg files. An interlaced file loads quickly at a low resolution and then becomes progressively clearer as the page continues to load. It makes sense to interlace large graphics if you believe the user needs to get an idea of the contents of the graphic quickly.
Users are usually more patient if they know for what they are waiting.
However, interlacing increases the file size slightly, so use it with discretion. For more information about Fireworks, see the IS documentation pages . If you do your photographic editing in Adobe Photoshop, you'll usually want to save your graphics in a .jpg format. In order to save a Photoshop file as a .jpg, you must compress any layers and be in RGB color mode. As from the file menu, and choose JPEG from the pulldown menu.