i still got trouble with flicker effect on a modal panel over an iframe containing a pdf document.

my modal panel is like this.

<?xml version="1.0" encoding="ISO-8859-1"?>
<ui:composition xmlns="http://www.w3.org/1999/xhtml"
 xmlns:ui="http://java.sun.com/jsf/facelets"
 xmlns:h="http://java.sun.com/jsf/html"
 xmlns:f="http://java.sun.com/jsf/core"
 xmlns:rich="http://richfaces.org/rich"
 xmlns:a4j="http://richfaces.org/a4j"
 xmlns:s="http://jboss.com/products/seam/taglib">


<rich:modalPanel id="edittabledatadlg" autosized="true" moveable="true"
keepVisualState="true" zindex="600"
 overlapEmbedObjects="true" rendered="true">
 <f:facet name="header">
 <h:panelGroup>
 <h:outputText value="Daten bearbeiten"></h:outputText>

 </h:panelGroup>
 </f:facet>

 <h:form id="tabledata">
 <rich:messages></rich:messages>
 <h:panelGroup id="idrowdata" layout="block"
style="background-color:white;z-index:550">
 <h:outputLabel value="Test" for="" />
 <h:inputText value="" />
 <h:outputLabel value="Test" for="" />
 <h:inputText value="" />
 <h:outputLabel value="Test" for="" />
 <h:inputText value="" />
 <h:outputLabel value="Datum" for="" />
 <rich:calendar value="" />
 </h:panelGroup>


 <h:panelGrid columns="5" style="float:right">
 <a4j:commandButton id="newrow" value="Neu"
 styleClass="rich-button" style="width:90px"
action="#{Page.tablerowadd}"
 reRender="idrowdata">
 </a4j:commandButton>

 <a4j:commandButton id="prevrow" value="Zurück"
 styleClass="rich-button" style="width:90px"
action="#{Page.tablerowprev}"
 reRender="idrowdata">
 </a4j:commandButton>
 <a4j:commandButton id="nextrow" value="Vor"
 styleClass="rich-button" style="width:90px"
action="#{Page.tablerownext}"
 reRender="idrowdata">
 </a4j:commandButton>



 <a4j:commandButton id="saverowdata" value="Ok"
 oncomplete="Richfaces.hideModalPanel('edittabledatadlg');"
 styleClass="rich-button" style="width:90px"
 action="#{Page.tablerowsave}" reRender="tabcurrentworkflow">
 </a4j:commandButton>
 <a4j:commandButton id="saverowdatacancel" value="Abbrechen"
 immediate="true" style="width:90px" action="#{Page.canceledit}"
 onclick="Richfaces.hideModalPanel('edittabledatadlg')"
 styleClass="rich-button" reRender="tabcurrentworkflow">
 </a4j:commandButton>
 </h:panelGrid>
</h:form>

 </rich:modalPanel>


</ui:composition>

<a4j:outputpanel id="docframe" style="z-index:0" >


<h:outputLabel value="" for="" />
 <s:link action="#{Download.getfile}" > <h:outputText value ="Datei
extern öffnen" />
 <f:param name="file" value="#{Page.masterdoc}"/>
 <f:param name="orig" value="#{Page.dokorigfilename}"/>
 </s:link>
 <h:outputLabel value="" for="" />


 <iframe src="#{WorkflowPage.masterdoc}" frameborder="1"
allowTransparency="true"
 style="position: relative; overflow-y: scroll; overflow-x:
scroll;z-index:0;border:1px solid #000000;background-color:transparent"
 height="787px" width="684px" />


</a4j:outputpanel>