title: Web Driver Selenium - Z-index Issue
body: <p>i have to make a test on a pop-up, i'm using WebDriver Selenium in Python.</p>
  
  <p>In few words if i open the pop-up, it goes under the overlay and it remains unclickable... but if i test this movement with WebDrivers Selenium everythings works.</p>
  
  <pre><code>popup = browser.find_element_by_id('help_paid_options')
  if popup.is_displayed():
      print 'Found'
  else:
       print 'Not Found'
  
  popup.find_element_by_xpath("//*[@id='help_paid_options']/*  [contains(@class,'x_pop_close')]").click()
  
  if popup.is_displayed():
       print 'Found'
  else:
       print 'Not Found'
  </code></pre>
  
  <p>How can i test that a element is clickable (truly).</p>