?????????????????????????????????
????selenium.common.exceptions.StaleElementReferenceException: Message: u'Element not found in the cache - perhaps the page has changed since it was looked up'
?????????????????????????cache??????????????????????????任??? ??????????????淢????????????cache?е???????????????????????
???????????????????λ?????????????????????a????????????????????????????????ε????????????????????????????????????????????????for loop??

length = len(driver.find_elements_by_tag_name("a")
for i in range(0??length):
links = driver.find_elements_by_tag_name("a")
link = links[i]
if not ("_blank" in link.get_attribute("target") or "http" in link.get_attribute("href")):
link.click()
driver.back()
??????????????η???????????????????????????a??????????cache?е?i????????????????????