What has changed that has messed up my Yahoo?

The word Yahoo has gotten very large with a very large advertisement that takes up almost 1/2 of my main page and I hate it. Everything else is moved down so far I have to scroll down to see it. Also there is no way to go from one message to another without either deleting the current message or going back to the inbox. How do I get back to the old way. Dennis Bennett denniswb01@yahoo.com