I understood that it would join the js together with the css to form one document

That would make for a great plugin indeed, especially if it caching of the results. Looks like there’s an update available. I suspect this would be relatively straightforward to implement as a plugin for anyone that has a clue about coding from scratch (e.g., not me!):
http://aciddrop.com/2008/01/23/site-speed-boost-script-updated/

Me neither!
... for anyone that has a clue about coding from scratch (e.g., not me!):
, BTW those php compressors sounds interesting http://aciddrop.com/category/php/
<!--[if lte IE 6]><link rel="stylesheet" type="text/css" href="assets/css/style_ie6.css" media="screen,print"/><![endif]-->
<!--[if gte IE 7]><link rel="stylesheet" type="text/css" href="assets/css/style_ie7.css" media="screen,print" /><![endif]-->
<?
$e= & $modx->Event;
switch ($e->name) {
case 'OnWebPagePrerender':
$path = $modx->config['base_path'] . "assets/plugins/acidDrop/";
include_once($path."class.compressor.php");
$options = array("javascript"=>array("cachedir"=>"/assets/cache/",
"gzip"=>true,
"minify"=>true,
),
"css"=>array("cachedir"=>"/assets/cache/",
"gzip"=>true,
"minify"=>true,
)
);
$compressor = new compressor($options);
$modx->documentOutput = $compressor->finish($modx->documentOutput);
break;
}
//Start things off
//$this->start();
function finish($content) //add content argument
//Echo content to the browser
//echo $this->content;
return $this->content;