improve search , investment and keep up to date. google has introduced so many new application introduced in last few years but yahoo is too slow.
Google is giving lots of very very important free service and if yahoo can open some free worthily service then it may be increase it's popularity.
I think its not possible for Yahoo now as Google and Bing are already going good. May be Yahoo needs to come with something new and cool like the Yahoo Messenger they have. The only thing I like in Yahoo.