Let's go to the daily chart to see what today did to the long-term charts. Here's the SPY, QQQ and IWN to see what happened
Several days ago I wrote the recent rally after the sell-off was suspect because of declining volume, but the declining volume may itself be suspect because it was coming down from a really high level. Well -- now we have confirmation. The rally was suspect.
You'll notice the same wording on each chart: big volume sell-off. Simply put, there were a ton of sellers in the market today, and they were looking to get out. They were willing to take a lower price to get out. That's one of the prime reasons for the drop.
Notice that technically, all the averages have a touch of breathing room -- but not much. Another bad day like today and the markets will be looking at a technical break-out on the downside.