I need a coupon plugin that can work in:
1. Firefox
2. Safari
3. Internet Explorer
4. Google Chrome.
Like couponalert.com.
Need to have skills in
For Firefox the language is mostly JavaScript and XUL (XML UI Language). Although it is possible to use Python and XUL, or even have compiled code bound trough XPCOM/XPconnect. But that's definitely not for beginners.
For Chrome the language is actually JavaScript, HTML and CSS. It's very similar to developing web application.