The numbers I have clustered over the last few candles represent the % difference between the 3EMA & the 9EMA. You could use any EMA's or MA's you choose I just happen to like these. The point is that since December of 2013, those two EMA's are getting closer together showing that upside momentum is weakening, and this is the exact same thing that happened in 2000 & 2007.
Is this chart a valid warning that the market may be getting ready for some kind of significant drop? I don't know and we're all going to have to wait until we see real evidence that the market is topping out. In the meantime, it's important to be aware of the potential move these negative divergences & loss of momentum could lead to.
For reference, bookmark the links below or do a screen capture.
Monthly chart of 2000 top: http://i1337.photobucket.com/albums/o663/StockMarketSystem/1999-2000MonthlyTop_zpsd0567f00.png
Monthly chart of 2007 top: http://i1337.photobucket.com/albums/o663/StockMarketSystem/2007MonthlyTop_zpsc10cb271.png