OpenX permission issue

Everytime when I login to my openx installation, I had this error message

Error: File permission errors detected.
These may impact the accurate delivery of your ads,
See the debug.log file for the list of unwritable files

This has to do with some of the file permission error. For my case, I just need to execute this two command to fix my problem

chmod -R a+w /home/openx/var/cache/
chmod -R a+w /home/openx/www/images/