title: WebDriverException: Message: 'geckodriver' executable needs to be in PATH
body: <p>os:windows 7
  selenium version 3.0.1
  mozilla firefox:48.0.2</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Users\LENOVO\Desktop\kk2.py", line 4, in &lt;module&gt;
    driver = webdriver.Firefox()
    File "C:\Python27\lib\site-packages\selenium\webdriver\firefox\webdriver.py", line 135, in __init__
    self.service.start()
    File "C:\Python27\lib\site-packages\selenium\webdriver\common\service.py", line 71, in start
    os.path.basename(self.path), self.start_error_message)
    WebDriverException: Message: 'geckodriver' executable needs to be in PATH. 
  </code></pre>
  
  <p>please give information step by step thoroughly please actually i am learner  </p>