Demo

You can easily create countdown page (teaser site, etc...).
http://sanographix.github.com/css3-countdown/demo/

Usage

1. Edit HTML

1. Edit h1, h2, and footer text.

2. Edit JavaScript

1. Set countdown limit (line:33)
2. (Optional) Add time's up message (line:36)

I created this countdown timer by using this script:
コピペでサクッと導入できるライブラリ非依存のJavascriptカウントダウン