To use the Image Optimizer to make an image with a transparent background:

  1. In the Web menu, select Image Optimizer.
  2. In the Image Optimizer dialog box, select the GIF file format button.
  3. In GIF Options tab, select the Transparency check box.
  4. Go to the Mask Options tab.
  5. Select "Pick color" in the Mask option and click "Add to Mask," then choose
  6. color directly from the preview window.
  7. Click "Save As" to save the optimized file.