PNGs create transparency in one of two ways. One of these methods employs the same approach used by GIFs, with a single color defined as transparent, and the other is to set an alpha channel . One of the advantages of PNG single-color transparency is that it doesn't remove a color from the available palette. However, the alpha channel is a much smoother method, as it is far better at blending colors, and allows you to select different levels of transparency in specific regions. The transparent areas of the PNG will blend and adjust naturally to whatever is behind the image when the background of the page isn't a solid white or black color.