In Jdeveloper 11.1.2 we often see that the designer is going off and looks clumsy without the ‘WYSIWYG’ feature during the design time. The jspx or jsff designer in Jdeveloper will show as

To fix this we directly go and delete this directory o.j2ee.jsplib in

C:\Documents and Settings\ USER_NAME\ApplicationData \JDeveloper\system11.1.2.0.38.60.17

Thanks to the blogger

For other version, if the file or folder does not exist then go to o.j2ee and delete or move – jsp-faces-tags-cache.xml and jsp-libraries.xml. Also delete .wlLib folder if it exists. If nothing works delete the system folder.

also make sure that the ‘Execute Tags in JSP Visual Editor’ is checked for adf components

updates from a collegue
If you have a class reference in your application folder that cannot be loaded this problem might occur

possible fixes

change

oracle.adf.view.rich.security.FRAME_BUSTING
<param-value>differentDomain</param-value>

To:

<param-name>org.apache.myfaces.trinidad.security.FRAME_BUSTING</param-name>
<param-value>differentOrigin</param-value>

or

change the class .adf/META-INF/services/oracle.adf.view.rich.context.ExceptionHandler
or rename this file oracle.adf.view.rich.context.ExceptionHandler