Question: Why does the new Yahoo homepage keep shifting between the old and the new ?? 

Answer: They are randomly choosing people to test out their BETA page before it goes live. Whenever you are chosen, you get to use the beta page for 1 week before it reverts back to the old. If you want to revert back to the old page before the 1 week is up, simply clear your cookies. Do this via Tools / Internet Options / Delete Cookies
This question from the Yahoo Q&A forum is categorized in the topic: Entertainment & Music