Search Wikipedia from any website
This is an oldie but goodie, that for sure works in Firefox...
Visit Conveniently searching Wikipedia, and follow the instructions for your browser. It's a bookmarklet that sits on your toolbar, and which serves as a Wikipedia search button that you can activate from any web page. The next time you want to look something up on Wikipedia while browsing a web-page, highlight the term and then click on your new bookmarklet.
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