Quick tip: Website loses focus while usertesting
Fellow usertesting.com enthusiasts might have encountered the problem when your website loses focus and the test subject misses out on something.
This widget is to be held responsible:
The problem is that this handy widget takes focus off from the browser. In this case the first click on your website only brings focus back to the browser. At this point test subjects often feel that they have clicked on the UI in vain. They continue their duties thinking that the current button is in fact inactive.
As symptomatic treatment until our friends at usertesting.com come up with a solution (eg. a browser extension) try detecting if your website/prototype has focus.
See demo below. Run the pen they try focusing outside the pen.