> pngcrush by Glenn Randers-Pehrson, available at http://pmt.sourceforge.net/pngcrush, is an open-source program that iterates over PNG filters and zlib (Deflate) parameters, compresses the image repeatedly using each parameter configuration, and chooses the configuration that yields the smallest compressed (IDAT) output. At the user's option, the program can explore few (below 10) or many (a brute-force traversal over more than 100) configurations. The method of selecting the parameters for "few" trials is particularly effective, and the use of a brute-force traversal is generally not recommended.
In addition, pngcrush offers a multitude of extra features, such as recovery of erroneous PNG files (e.g. files containing bad CRCs), and chunk-level editing of PNG meta-data.
In the end it does not matter since they did not use any of them. If I can reduce size of that page in 2 minutes, without any webdev background and using the only tool I could remember if few seconds than there is something seriously wrong with the way they treat visitors.
