Chrome用　Sleipnir用
https://chrome.google.com/webstore/detail/remove-scrollbars/lkfmjedfjkmfmckgcadelnfjebccjdcf/related?utm_source=chrome-ntp-icon
Firefox用　Lunascape(Gecko)用
https://addons.mozilla.org/ja/firefox/addon/hidescrollbars/
SoftTilt 横スクロール(参考)
http://www.vector.co.jp/soft/dl/win95/util/se347519.html