This addon adds a sidebar which, when opened, displays tweets that talk about the page you're on.
It uses the Topsy service's API, which works with both shortened and long URLs. The sidebar stays in sync with the page it was opened on while you browse, periodically checking for updates. There's also a button in the sidebar that allows you to re-sync to a different page.
The preferences "window" is integrated into the sidebar. Click the down arrow in the upper-right corner to open the preferences, and click it again to close them. This window shows the URL that the sidebar is currently synced with, how many older tweets the "more" button will fetch, how often to check for new page-specific tweets, and whether or not to fetch only "influential tweets".
Note: There is currently no keyboard shortcut to show/hide the sidebar, though I have added a toolbar button that will do this (you have to "customize" your toolbar to add it).
PS - Yes, this addon was indeed inspired by Twitter Reactions, but has no relationship to it. It was independently developed.
This addon is not associated in any way with the website, pagetweets.com
Due to lack of interest, this addon is no longer supported and will not be updated for future versions of firefox.