PNG (pronounced "ping") is the [Acronym] for Portable Network Graphics, a new, losslessly compressed bitmapped graphics format. It is approved by the [World Wide Web consortium|W3C] as the successor of the [GIF] format. The latter depends on a compression algorithm called LZW which was patented by [Unisys] long ago. In contrast, PNG relies on the patent free LZSS algorithm for compression and is completely unencumbered with licensing fees. 

  

 Recent versions of [Mozilla], [Opera], and [Microsoft] InternetExplorer support PNG, although the latter doesn't support alpha channels natively. Rumour has it that the IE engine is too old and out of date to support transparency without lots of hideous hacks. Amusingly(?), while Microsoft can't make these hideous hacks, [we can|http://support.microsoft.com/default.aspx?scid=kb;en-us;Q294714]. Since that way is completely incompatible with every other browser on the world, you should [use a slightly different approach|http://webfx.eae.net/dhtml/pngbehavior/pngbehavior.html].