後で調べる

<del>や<s>の打ち消し線がFirefoxだけ出ない。

• OK safari4.0.2
• OK chrome2.0.172.39
• OK IE8.0
• OK opera9.64
• NG Firefox3.0.12
• NG Firefox3.0.12 safe-mode
• NG Firefox3.5.1