To complete integration we open Dropbox login form in a new window. Since you will enter your Dropbox password, it should be in a new pop-up window so you can see that the domain name of the site is dropbox.com.

On one of our Usertesting.com tests, a tester clicked on the button and nothing happened. She did not see the "enable pop-ups" message on the browser and was not able to complete the integration. That's why we added a check to see if the user has problems with opening the window and we show that warning message.