warning: is_dir(): Stat failed for sites/default/files/css (errno=13 - Permission denied) This is a theme related error message in drupal cms. Although there is no files or directory in files folder named css but why this error is called. I think there is some problem in permissions in the files directory. Change it to 777 can solve the problem. The drupal SKY FOLIAGE themes are some of the example. I uses drupal pixtue-reloades theme. This theme works nice for me, it has color selection as like as garland so i can change my site color quite open. The color scheme saved in drupal files folder cache.

Some related warning list

* warning: is_file(): Stat failed for sites/default/files/.htaccess (errno=13 - Permission denied) in /hsphere/local/home/weisswol/drup6.esites4u.biz/includes/file.inc on line 127.
* warning: fopen(sites/default/files/.htaccess): failed to open stream: Permission denied in /hsphere/local/home/weisswol/drup6.esites4u.biz/includes/file.inc on line 129.
* Security warning: Couldn't write .htaccess file. Please create a .htaccess file in your sites/default/files directory which contains the following lines:
SetHandler Drupal_Security_Do_Not_Remove_See_SA_2006_006
Options None
Options +FollowSymLinks
* warning: is_dir(): Stat failed for sites/default/files/logo.gif (errno=13 - Permission denied) in /hsphere/local/home/weisswol/drup6.esites4u.biz/includes/file.inc on line 102.
* warning: is_file(): Stat failed for sites/default/files/.htaccess (errno=13 - Permission denied) in /hsphere/local/home/weisswol/drup6.esites4u.biz/includes/file.inc on line 127.
* warning: fopen(sites/default/files/.htaccess): failed to open stream: Permission denied in /hsphere/local/home/weisswol/drup6.esites4u.biz/includes/file.inc on line 129.