Fair enough, but if you want to compress CSS, JS and HTML then why not test it on those? It also depends upon how you are supplying the compressed data. For st

Fair enough, but if you want to compress CSS, JS and HTML then why not test it on those? It also depends upon how you are supplying the compressed data. For static files, the compression time might not even matter - the web server can cache all the compressed versions and the compression performance is minimised. For dynamic data (e.g. the output of a PHP or whatever), you might also want to test how well the compressors handle streaming data, e.g. feeding parts of a page piecemeal into the compressor and directly sending the output to the client packet by packet. Some compression systems handle this extremely badly.