How to prevent anonymous users not viewing any webform content
You'll have to look at the content_access module which will allow you to configure default access control on a per node type or per node basis.

Content Access:


  This module allows you to manage permissions for content types by role and author. It allows you to specifiy custom view, edit and delete permissions for each content type. Optionally you can enable per content access settings, so you can customize the access for each content node.