There are some solutions to change de webui-jsf.jar library to hardcode the URL, since this is not the best solution, because you have to create a patch for every project (even create a patch if you move the project from test to production envoirement).

So i’ve looked in the code (shipped with Netbeans) and made a little fix. I determine the server URL from the HttpServletContext.

My fix:

Edited com.sun.webui.jsf.util.JavaScriptUtilities

The following method is little bit changed to determine the jsFile String

   private static void renderJavaScriptInclude(UIComponent component,
            ResponseWriter writer, String file) throws  IOException
        if (file == null) {
            return;
        }
        String baseURL = "";
        try
        {
            HttpServletRequest req = (HttpServletRequest)FacesContext
                 .getCurrentInstance().getExternalContext().getRequest();
            StringBuffer url = req.getRequestURL();
            baseURL = url.substring(0, url.indexOf("/",10));
            // HTTPS fix over LB
            if (baseURL.indexOf(":443") >0)
            {
                baseURL = baseURL.replaceFirst("http://", "https://").replaceFirst(":443", "");
            }
        }
        catch (Exception e)
        {
            baseURL = "";
        }
        String jsFile = baseURL + getTheme().getPathToJSFile(file);

You can also download the patched jar file and put it in your netbeans directory/visualweb2/modules/ext/

Finally some annoying bugs are fixed now. Visual Designer ICEfaces (Netbeans) works almost like a charm now.
There are some small things missing (like effects) but these things are easlily to work around in JSP edit mode.

Download here