When you know the background color of the web page on which an image will be displayed, you can use the matting feature to fill or blend transparent pixels with a matte color that matches the web page background.
To keep fully transparent pixels transparent, and blend partially transparent pixels with the matte color, select Transparency. This option prevents the halo effect you see when you place an anti-aliased image on a web page background that differs from the image background. This option also prevents the jagged edges of hard-edged transparency.
To fill transparent pixels with the matte color and blend partially transparent pixels with the matte color, deselect Transparency.
Eyedropper Color (to use the color in the eyedropper sample box)
White, Black, or Other (to select a color using the Color Picker)