The error massage is saying that the public_html/images/lg folder does have the proper permissions.
You may be able to modify the permissions using Dreamweaver, if not you will need to use an FTP program, or your host may have a website management utility that allows you to change permisions on folders.
In Dreamweaver, open the File Panel. In the view Select List, select Remote View.
Right Click the public_html/images/lg folder and select Set permissions.
The Owner must have Read, Write and Execute permissions.
For the User/group and Everyone, Read, Write should be sufficient.