After installing the add-on, before clicking a link, just hover over your mouse it, an icon (site’s fav icon) will appear. Rest your mouse on the icon, a popup window appears with an enhanced summary of the linked page.
This is not just a link preview tool, it is more than that - Lets you know sizes and dates of linked files, lets you submit a link or selected text to del.icio.us, Google Bookmarks, Digg or Reddit, etc, you can email the link and contents to anyone and more.
Interclue is fast and does not find any load on Firefox. There are several options available to customize the tool. For example, you can add any words in the ‘Words lists’ (In Firefox Tools – Interclue options – Advanced – Safety), any URLs containing those words and having the same domain as the current page will not be fetched without your explicit permission.
Interclue is compatible with Firefox 3.0 – 3.5 and works with any sites. Download Interclue.