HTML5的格式  <!DOCTYPE HTML>

HTML5浏览器的支持  

header, section, footer, aside, nav, main, article, figure {
    display: block;
}

添加一个自定义的HTML新元素

<script>
    document.createElement("myHero")
</script>

display: block;
    background-color: #ddd;
    padding: 50px;
    font-size: 30px;
}