using 1.51 zen cart
please anyone can help for these error :

"Can not create file "/home/webusers/xxxxxxxx/xxxxxxxxxxxx.com/www/sitemap/sitemapmainpage.xml". You may need to use your webhost control panel/file-manager to change the permissions effectively."

i did set the permission for folder sitemap xml to 777 already but still can not get the right thing, please help.....thanks.