Huh? Don't you think it is just because you're viewing a cached version in IE? Try enabling check for updates on the website everytime you visit the website.
There isnt anything new as far as I know, try clearing your cache for both IE and Firefox and check again
Yes yahoo have been testing a new homepage, you can change it back to the old one by clicking the option change back to the classic yahoo webpage.
They randomly test out the new one. I've viewed it at random points in time while visiting their site.
You can see the new Yahoo Home page here http://kara.allthingsd.com/20080917/a-first-look-at-the-new-yahoo-homepage-redesign-apps-rule/