The S&P 500 is looking to bounce ahead of the open today, with futures pointing higher by 0.8% currently. After all the noise surrounding the Fed decision yesterday, I would highlight the technical picture is worth paying attention to here.Stocks sold off yesterday after the Fed raised interest rates by 25 bps to 3.75% - 4.00% and signalled that further tightening remains on the table. The decision itself was unanimous, while 16 of 18 policymakers are projecting at least one more rate hike before the end of this year.That was enough to rile markets up initially, but the more interesting bit for stocks is arguably where the selling stopped.The S&P 500 bounced right off its 100-day moving average (red line), which is sitting around 7,510 on the chart. That also comes close to the 23.6 Fib retracement level near 7,463, giving buyers a fairly obvious technical region to lean against. And for now, they are doing just that.Looking to the open today, equities are breathing a little easier with futures holding higher. That is helped by a steadier showing in long-term Treasury yields and softer oil prices, taking a little pressure off valuations after the Fed's hawkish message.From a technical perspective, though, I would not get too carried away just yet.The immediate challenge is for the S&P 500 to reclaim the 7,600 region, which provided some semblance of a support region before giving way. A move back above there would make the bounce look more convincing and put the recent highs near 7,800 back into view.If buyers cannot manage that, then this could still prove to be little more than a technical rebound.But as traders and investors continue to digest the Fed decision, the 100-day moving average is the key line that I'll be watching. If the bond vigilantes return and send yields back above 5%, that will be a quick catalyst for stock market sentiment to shift to the other end.The danger is on a sustained break below the 100-day moving average, which would weaken the technical setup considerably and expose the 7,300 level next.In short, the bulls have found support where they needed to for the time being. Now, they need to show they can actually build on it or risk an uglier selloff. This article was written by Justin Low at investinglive.com.