title: How to press 'Enter' without targeting a WebElement
body: <p>I make tests with WebDriver and at a moment a popup appears, with no fixed attribute (auto-generated).</p>
  
  <p>So, the simplest way (I think) is to press the key 'Enter' on the keyboard.
  But I can't find the way to say 'Just click on the browser, not on an element of the browser'.</p>
  
  <p>It's possible with WebDriver? How can I achieve it?</p>