I solved the above CDN-related issue by editing the line 101 of the combineit.php as follows:
Code:
$buffer = str_replace($first, '<link type="text/css" rel="stylesheet" href="'.'http://cdn.example.com'.'/cache/'.$hash.'.css" />'."\n", $buffer);
However, I came across an issue with WYSIWYG editor and FireFox web browser. When css files, including inline css, are combined, the WYSIWYG editor is not styled in FireFox (the background is gray instead of white, and fonts are different, too).
I think if it were possible to exclude individual css file(s) from being combined, this issue could perhaps be corrected by excluding vbulletin_editor.css. But I don't know if it would at all be possible to modify this product to exclude individual css files like it is possible to exclude js files.
Any feedback would be much appreciated.