<aside>
asideの使い方が紹介されてました。
<aside> says nothing about presentation, it’s purely a semantic construct. It marks up sections that are not part of the main text. This is the kind of text that is written in green text in the HTML5 spec itself, for instance, or that is written in sidebars in magazines, or in popup windows in some applications.
ポップアップウインドウまで！へー
