Error on LAMP server

It depends - it's the Apache user that you want to give write access to, so you could change the owner of that directory to 'apache' or you could give folder 0777 rights.

It's best practice so move application out of public_html folder, same goes for all writable asset folders.

Code:

/application <-- all your CI stuff
/cache <-- session files
/system <-- CI system folder
/public_html
    /index.php <-- this is where your domain points to
    /css <-- domain css files