Works with CiviCRM 4.4. It might not be supported anymore.
On Contribution public forms, if the confirmation page is disabled, it will instead display a popup confirmation before submitting the form.
Screenshot (click to enlarge)
Releases
Since CiviCRM 5.x, extension releases compatible with CiviCRM 5.0 are compatible with 5.0 and later. An extension release compatible with 5.25, for example, means that it requires CiviCRM 5.25 or later.