VRichTextarea iframe customization issue in firefox

Assalamu alaikum,

I customized client side of RichTextarea component for styling its iframe and customizing its toolbar actions, this customization seems has been succeed in
chrome
but in
firefox
not succeed .



public class VMyRichTextArea extends VRichTextArea {

	private Document IframeDocument;

	public VMyRichTextArea() {
		super();
		sinkEvents(Event.ONCLICK);
	}

	@Override
	protected void onAttach() {
		super.onAttach();
		initIframeDocument();
		initIframeStyle(contentDocument, generateBaseStyleClasses());
		addIframeBodyEventHandler();
	}

private void initIframeDocument() {
		NodeList<Element> iframes = this.getElement().getElementsByTagName(
				"iframe");
		if (iframes != null && iframes.getLength() == 1) {
			IFrameElement iframe = (IFrameElement) iframes.getItem(0).cast();
			IframeDocument = iframe.getContentDocument();
		}
	}

private native void initIframeStyle(Document doc, String value)
/*-{
	    var el;
	    var elid = "myrichtextarea-style";

	        el = doc.createElement("style");
	        el.type = "text/css";
	        el.id = elid;
	        doc.getElementsByTagName("head")[0]
.appendChild(el);

	    if(el.styleSheet){
	        el.styleSheet.cssText = value;
	    }else {
	        if(el.firstChild){
	            el.removeChild(el.firstChild);
	            }
	        var rules = doc.createTextNode(value);
	        el.appendChild(rules);
	    }
	    }-*/;

.
.
.

This is the outline part of my code.

Is there any solution for that?

Sorry for my bad English.

Could any one explain what happens to contents of ifram when set new value to richtextarea?

Thanks