Mozilla bows to criticism of removing the status bar, now by default shows link Target URL at the bottom in a tooltip in latest Firefox 4 Beta 12 version. This change will affect Firefox 4 final version also. If you got used to view URLs in location bar with mouse over, then Link Location Bar Add-on enables that feature for Firefox 4 again.
After installing this add-on hovering mouse over on link URL will be shown in the location bar than at the bottom. To get the default behavior you need to disable or uninstall this add-on.