lossless png compression

If google or any yslow optimizer is asking to compress png using a lossless method => a good approach is this program, cli, very simple: optipng.sourceforge.net

ie in windows, fire a cmd and write: optipng.exe -u 1 filename

it will save up to 75-80% of a png file (if it was 1mb, it will be 200kb!) without affecting at all the quality. The “magic” is that web browsers support a special kind of compression that neither photoshop or the pc support. if you open a compressed png in photoshop it will look awful..