When the MainJSP property is set to true, it indicates that you want to use the page specified in the JSP property for the login page. When this property is set to false, which is the default value, the nidp.jsp is used for the login page. If you use two methods to create a contract, this property must be set to the same value on both or set on only one. When it is set on only one method, the value is applied to both.
Property Name: MainJSP
Property Value: true
For information about creating a custom login page, see Customizing the Identity Server Login Page.