The free Headup add-on for the Firefox Web browser displays a pop-up overlay of information when you select a specific word on a Web page, or hover your mouse over a word it underlines on selected sites. The beta extension can pull in personalization information from Facebook, Gmail and other online services.
There are four ways to bring up the Headup display. First, you can underline any word on a Web page, right-click and choose 'headup this.' Also, on supported sites like Facebook or Last.fm, headup will underline certain words that you can mouseover for a pop-up.
On Google search result pages, you'll see a line at the top with Headup: [search term] that you can mouseover. And finally, you can click the headup icon in the lower-right corner and get a pop-up with information it finds from tied-in services (like Facebook), along with things like recommended videos.
The Headup display, which uses Microsoft's Silverlight, can expand to display photos, videos and extra info directly within the popup, and the information it offers varies depending on the keyword. You might see a summary, search results and other sub-headings for a word you select; you might get listings of a Facebook friend's favorite TV shows and films if you mouseover his or her name on your Facebook page.
You might enjoy some of the info listed for some items, such as CDs on Amazon.com. The Headup link for one CD listed the playable snippets for each track, along with the lyrics.
But in other cases the Headup display might not be especially useful. If you have a page full of Google search results for a particular term, you're probably better off sifting through those results rather than detouring to the Headup link. And if you're already on Facebook and want information on a linked-to friend, you can click the link to get the friend's full page instead of the partial info in the Headup display.