Go to the Twitter Buttons page:
https://about.twitter.com/resources/buttons#tweet
Click the Tweet button in the “Preview and Code” section. Tweet dialog opens up, with referer, text and other params in the URL.
Click “Tweet” in the dialog. Dialog window RELOADS and removes all URL params from dialog URL. NO TWEET IS POSTED.
Click “Tweet” button again in the dialog. Tweet is sent.