CSS is not aggregated anymore - how to debug? On a rather complex Drupal 6 site (multi domain etc.) CSS files are not aggregated anymore and CSS style definitions appear directly inside the HTML pages.  The output of ´drupal_get_css´ is ok, but when I installed the Advanced CSS/JS Aggregation module, I see that the module reports the aggregated css files as Missing files.  But when these files are opened manually, they are ok.  The problem itself is not related to the the advagg-module, I only enabled it for debug reasons.

I have not switched themes on the site affected, but I have been playing around with a new theme (mobile jquery) and a correcponding jquerymobile module on a different module from the same installation.  I do not currently think, that the problem has been caused by this module.

I guess the problem is caused by some module weights, but I am having trouble debugging the theming process.  I am looking for help, where I should start debugging, why the aggregated CSS files are not used.

Update:
I have edited drupal_add_css to default to not preprocess files.  The difference is, that each css-block is inserted in a seperate style statement, whereas right now, only a single aggregated CSS style statement is generated.  So I am really tryng to find out, why I am ending up with the long css style definition, instead of a link to the aggregated stylesheet.
I am extremely sorry, but I have found out that the problem was not caused by Drupal.  It seems that the a proxy has been installed by the ISP that automatically compresses pages and rewrites stylesheets to be included into the page directly.  

The pages work correctly when being fetched via other networks.