[Simon]

Yep, a very good tip, and works well for javascript files too. The real benefits of compression come from compressing these type of files in my opinion, not simply the html.

If you have a large number of js / css files in a directory and don't want to change them all (ie. feeling lazy ), you can add 2 files to the directory that will do the job for you (needs htaccess access and zlib enabled):

.htaccess

AddHandler application/x-httpd-php .css
php_value auto_prepend_file css.php
php_flag zlib.output_compression On

css.php

<?php 
header("Content-type: text/css; charset: UTF-8");
header("Cache-Control: must-revalidate");
header("Expires: " . gmdate("D, d M Y H:i:s", time() + 3600) . " GMT");
?>

You can change css to js to get the same results with javascript files.