Try adding this code in Theme Options > CSS
Please note that what you did here is custom. We can't guarantee that it will continue to work in the future and in case or in that event, you'll need to forward this to a third party developer because fixing customization issues is not a part of our support service. Please see our Terms.
The method that we support for this case is using one of our bundled grid plugins. Please see our Knowledge Base for more details.