If you want to point a finger at the most recent drops in the DOW or the NASDAQ then look no further than the earnings statements of their respective companies.
Now, you can get early warning on what these all important earnings will be like. They call them "earnings whispers" and they are supposed to be gleaned from insiders and others who know the real deal.
There are free sites all over to get this data, but I use this one as the first step to finding out what's coming for my investments.
The site below free. re-type it and take out the s p a c e s: