I created a Enterprise wiki site in SharePoint 2010 but when i create a page,the Wiki Categories field is greyed out and disabled. The Managed Metadata service is already started and the taxonomy feature is activated. in Central Admin -> Manage Web Application --> My app --> Service Connections , the Managed Metadata service is available and checked. When i create an other web application and create a wiki site, it works fine (in the new web application), but i can't delete my web application because it is in production. Any help please?