Also here:One last thoughtful touch in the Slice palette is the "No Image" option. You can tell the slice to contain no imagery, and then assign a background color to it. In essence, you can use ImageReady to get the browser to draw part of your graphic for you by replacing a solid color image with a table background color.
ImageReady, by default, creates a single Auto Slice for every image you open. However, there is a button on the ImageReady toolbar that allows you to toggle the Slice view on.