Steps to reproduce (in netbeans):
  Creating an app with a WebView loading the page (http://docs.oracle.com/javafx/)
  Set the netbeans project properties to:
    Sign the app
    Run the app in a browser
  Run the app in NetBeans (will launch browser with embedded app).

The following error is printed to the NetBeans output window multiple times:

java.net.MalformedURLException: unknown protocol: javascript
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at sun.plugin2.message.helper.URLHelper.read(Unknown Source)
at sun.plugin2.message.CookieOpMessage.readFields(Unknown Source)
at sun.plugin2.message.transport.SerializingTransport.read(Unknown Source)
at sun.plugin2.message.Pipe$WorkerThread.run(Unknown Source)

Attached sample NetBeans project which replicates the issue.