selenium对象标识在同一窗口中从一个页面导航到另一个页面时出现问题

While navigating from one webpage to another web page in same window the selenium is showing that no such element is found on second page. For example it is able to find the objects till login page after successful login it is not recognizing the objects. Kindly tell me why this is happening and what is the solution of it. For the second Method i am facing the issue. I used thread. sleep and switch window still facing the problem.While navigating from one webpage to another we