自动化测试 - python selenium，当前窗口跳转在返回原页面，cache被清空

需求：
1. 获取页面上指定的多个链接，并依次点击
2. 点击在当前窗口跳转到目标页面之后，“后退”到原始页面
3. 在原始页面上继续点击后续的链接

因为当当前页面发生跳转之后，存在cache中的关于这个页面的元素也被清空，所以参考：http://www.cnblogs.com/harolei/p/3464403.html 这个改了下

但执行到‘line.find_element_by_class_name("result-class").click()’这步是报错，提示：
Traceback (most recent call last): File "click.py", line 87, in line.find_element_by_class_name("result-class").click() File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webelement.py", line 255, in find_element_by_class_name return self.find_element(by=By.CLASS_NAME, value=name) File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webelement.py", line 411, in find_element {"using": by, "value": value})['value'] File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webelement.py", line 404, in _execute return self._parent.execute(command, params) File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 195, in execute self.error_handler.check_response(response) File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/errorhandler.py", line 170, in check_response raise exception_class(message, screen, stacktrace) selenium.common.exceptions.NoSuchElementException: Message: Unable to locate element: {"method":"class name","selector":"result-class"} Stacktrace: at FirefoxDriver.prototype.findElementInternal_ (file:///var/folders/wj/6lkd2_7x0flgks_8ycttq_j00000gn/T/tmpUKXnLL/extensions/fxdriver@googlecode.com/components/driver-component.js:10299) at fxdriver.Timer.prototype.setTimeout/<.notify (file:///var/folders/wj/6lkd2_7x0flgks_8ycttq_j00000gn/T/tmpUKXnLL/extensions/fxdriver@googlecode.com/components/driver-component.js:603)

一直没找到解决办法...，原始代码如下：

        browser.implicitly_wait(10)

        browser.get("http://m.baidu.com")
        time.sleep(1)
        browser.find_element_by_id("index-kw").send_keys(word)
        browser.find_element_by_xpath("/html/body/p[1]/p[1]/p[2]/form/p[1]/p/button").click()

        '''暂停5s'''
        time.sleep(1)

        length = len(browser.find_elements_by_class_name("result"))

        for i in range(1,length):
            lists = browser.find_elements_by_class_name("result")
            line = lists[i]

            line.find_element_by_class_name("result-class").click()
            browser.back()