One advantage of using CSS to make an otherwise rectangular (really, square) image appear circular is that the underlying images won't become obsolete if the vi

One advantage of using CSS to make an otherwise rectangular (really, square) image appear circular is that the underlying images won't become obsolete if the visual design changes to shift away from circular images. Another is that commonly used lossy image codecs perform poorly on sharp transitions, and block-based compressors perform especially poor on rounded corners, and often, with transparency.