Question

I’ve used XUL to create a toolbarbutton. When I click on this button, I want a div to popup in the same style as clicking on an extension in Google Chrome. How can I accomplish this?

Answer 1

If you want to add HTML elements to XUL document, you have to define the namespace for it:

<window
  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
  xmlns:html="http://www.w3.org/1999/xhtml"
>

Then you can add HTML elements, but you have to prefix the tag names with the namespace. Like this:

<vbox>
  <description>This is XUL element</description>
  <html:div>This is HTML element</html:div>
</vbox>

You can find more info and examples in the official documentetion at Mozilla Developer Network.