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The main point to note with all three charts below is prices are approaching or are directly on the upward sloping trendline that started in early March. That means we are at technically important levels. In addition, we have two more days for this week and traders may not want to hold positions over a two day weekend. Also remember we are in the middle of earnings season, possibly adding to the hair trigger of traders. Finally there is the basic question of whether or not the economic fundamentals support the current market rally.
In the event of a sell-off (which would be a natural development considering the run we've had) there are plenty of technically important support levels. Those are in the second series of charts which include all the simple SMAs along with Fibonacci levels and various other technically important levels.
Technical support levels for the SPYs, QQQQs and IWMs