I’m currently taking a look at Greasemonkey scripts in general. I always thought that it would be to complicated to install and use them which is absolutely not the case to my astonishment.
Look it up is another Greasemonkey script that can be installed like any other Firefox extension. It becomes active once you reboot Firefox and works twofold. First you mark a word or phrase in Firefox and hit a key afterwards to send a request to a dictionary site such as wikipedia.
The result is displayed in the same window that you marked the word in. It will be displayed on the right side by default but this can be changed. Almost everything can be changed. You can select different keys that trigger a search and add new sites to Look it up. It is also possible to change existing ones, if you prefer for instance the French Wikipedia service you can easily change the url of the Wikipedia entry to the French version.
Last but not least you can change the way the results are shown on the website. You can change size, appearance and everything else by using css. The default settings are fine nevertheless and only few users really need to change anything here.
Look it up immediately in Firefox » gHacks tech news
Look it up immediately in Firefox 
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