How do I tell Drupal not to aggregate my css file
To stop a file being aggregated, you can add a flag to the drupal_add_css() command which loads the file. To do this, hunt where the CSS is added and add array('preprocess' =&gt; FALSE) after the style, e.g.

drupal_add_css('/fonts/fonts-min.css', array('preprocess' =&gt; FALSE));


Alternatively, external CSS are never compressed, so if you change the CSS to the absolute URL of the file it won't be compressed.

drupal_add_css('http://mysite/css/fonts-min.css');


If you want to change a CSS included from a .info file, it might be best to add it as an external file with _preprocess_html in template.php. This is well explained under 'Adding external stylesheets' on this page.