>>> br=webdriver.Firefox()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\Python27\lib\site-packages\selenium\webdriver\firefox\webdriver.py", line 103, in __init__
    self.binary, timeout)
  File "D:\Python27\lib\site-packages\selenium\webdriver\firefox\extension_connection.py", line 51, in __init__
    self.binary.launch_browser(self.profile, timeout=timeout)
  File "D:\Python27\lib\site-packages\selenium\webdriver\firefox\firefox_binary.py", line 67, in launch_browser
    self._start_from_profile_path(self.profile.path)
  File "D:\Python27\lib\site-packages\selenium\webdriver\firefox\firefox_binary.py", line 90, in _start_from_profile_path
    env=self._firefox_env)
  File "D:\Python27\lib\subprocess.py", line 710, in __init__
    errread, errwrite)
  File "D:\Python27\lib\subprocess.py", line 958, in _execute_child
    startupinfo)
WindowsError: [Error 2]

请问这个怎么解决呀？