However PNG can include an 8-bit Alpha channel which allows variable transparency and a range of special effects, though use of these may not concern image archive creators. It is claimed that this form of interlacing enables text within a PNG image to be readable in half the time that it would be when using the GIF format, which uses one dimensional interlacing. One dimensional interlacing slowly reveals the detail of an image in finer and finer detailed rows from top to bottom. Two dimensional interlacing reveals the image in finer and finer resolution vertically and horizontally at the same time. Browser Support of PNG Browsers supplied by Netscape and Microsoft still do not fully support PNG .
Support is better than it used to be but there are still a number of minor problems or bugs.
The problems are mostly to do with support, or non-support, of variable transparency. The Web browser vendors are addressing these problems and claim that their future releases will fully support the PNG format. Microsoft seem to be slower at implementing full support. Its extremely efficient compression algorithm has enabled fast transport of 24-bit photographic type colour images over the Internet while the GIF format, the only other standard available for Web images, allowed only up to 256 colours in an image. It is also intended that the functionality of the format be increased with the inclusion of more features than the previous standard.