Aliased Image The edges of this world image are aliased (masked) so it fits seamlessly on top of any web page background color or pattern. Anti-Aliased Image The image above is not aliased, or masked, so note the somewhat ugly (white edge) around the image. However, if you were to place this image on a white backgound, that white edge effect would be invisible. Also, images with drop shadows, glows or other special treatments are unsuitable when aliased, and are best used on a white (or very light) background color.