Also about the waiting. Sometimes there is a few seconds of waiting before the Invoice loads or the form gets submitted. Well sometimes this is a bit slow. It caused few users to close before the page loads. I’ve seen this in other web services as well. The easy, effective and widely used solution is to add the loading bar. That way users know something is loading and not to close the browser.
The worst thing is waiting and not knowing if it works, is it stuck. Especially with the money transactions.
