MDN wants to learn about developers like you:

Note: This page documents the Jetpack Prototype, which is  no longer under active development. Read the experiment report for what we learned from it and the blog post announcing the first SDK release for what we're up to next!
Page modifications
Greasemonkey!  Execute callbacks when certain pages are opened
Allows a jetpack to empower a domain with extended abilities beyond those native to web pages

Document Tags and Contributors

 Contributors to this page: Sheppy, MykMelez, adw, Aza
 Last updated by: Sheppy,