What are Stylesheets Stylesheets can be applied in three ways Attached to solution Attached to solution interface Default application stylesheet Stylesheets are defined in: Designer > Ressources > Stylesheet Stylesheets contain CCS code to markup the page elements. The stylesheets may inherit content from each other, which is spcecified by the  Parent stylesheet . Parent stylesheets are automatically preprended to the stylesheet in question, so definitions may be overloaded if needed. A good ressources for learning CSS can be found here:  http://www.w3schools.com/css/ The default stylesheet for the application is defined in the policy:  defaultStylesheetID