I tried to make a yii project for testing by executing
/var/www/html/yii/framework/yiic webapp demo
and when I go to localhost/demo I get en er
If u r sure file permissions set correctly for the folder and still u getting the error, disabling SElinux or add an exception for SElinux is working if u r using CentOS.
edit /etc/selinux/config file
for disable SElinux or run this command for add an exception
sudo chcon -t httpd_sys_rw_content_t /path/to/ur/annoying/folder -R