How to remove default theme from Java Faces application

<jsp:root version="1.2" xmlns:f="http://java.sun.com/jsf/core" xmlns:h="http://java.sun.com/jsf/html" xmlns:jsp="http://java.sun.com/JSP/Page" xmlns:ui="http://www.sun.com/web/ui">
    <jsp:directive.page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8"/>
        <f:view>
            <ui:page id="page1">
                <ui:html id="html1">
                    <ui:head id="head1">