void beginRender(MarkupWriter writer) 
{
        if (tracker == null) throw new RuntimeException(InternalMessages.encloseErrorsInForm());
        if (!tracker.getHasErrors()) return;
        writer.element("div", "class", className);
        // Inner div for the banner text
        writer.element("div");
        writer.write(banner);
        writer.end();
        List< String > errors = tracker.getErrors();
        if (!errors.isEmpty())
        {
            // Only write out the < UL > if it will contain < LI > elements. An empty < UL > is not
            // valid XHTML.
            writer.element("ul");
            for (String message : errors)
            {
                writer.element("li");
                writer.write(message);
                writer.end();
            }
            writer.end(); // ul
        }
        writer.end(); // div
}