Customizing the download progress bar - Archive of obsolete content
ile, add the following (replacing "myextension" with the name of your extension's chrome package): % overlay chrome://mozapps/content/downloads/downloads.xul chrome://myextension/content/downloads-overlay.xul in downloads-overlay.xul, reference the new stylesheet: <?xml version="1.0"?> <?xml-stylesheet href="chrome://myextension/skin/myextension.css" type="text/css"?> <overlay id="mydownloadoverlay" xmlns="http://www.mozilla.org/keymaster/gat...re.is.only.xul"> </overlay> in jar.mn, make sure that there is an asterisk in front of the entry for myextension.css so that it will be preprocessed.

XUL Changes for Firefox 1.5 - Archive of obsolete content
loading overlays dynamically xul now supports loading overlays dynamically with the document.loadoverlay function.

XUL Overlays
loading overlays at runtime firefox 1.5 and other gecko 1.8-based applications also support loading overlays on-the-fly via the document.loadoverlay() function.

Document - Web APIs
document.loadoverlay()obsolete since gecko 61 loads a xul overlay dynamically.