The issue here manifests itself as refreshing (in Chrome) lose the CSS. This issue appears to be specific to Litespeed, and as far as I know, they've acknowledged it as a bug and have a patch.
However, in XenForo, you can change library/XenForo/CssOutput.php:
to:
However, in XenForo, you can change library/XenForo/CssOutput.php:
Code:
header('HTTP/1.1 304 Not Modified', true, 304);
Code:
header('Content-type: text/css; charset=utf-8', true, 304);