New Feature: It is now an option to disable double-clicking and launch the dictionary only by highlighting and right-clicking on the word.

Fixed bug in text-formatting

Improved readability.

Update: You can now try the dictionary add-on with a built-in demo key. Note that the add-on might run a little slower with the demo key, and there is a limitation on the frequency of use. Also note that all add-on's are disabled on this page by Mozilla :)