In their statement, the Fed acknowledged that the domestic as well as international economic situation has deteriorated markedly. They drastically revised down their 2012 growth interval from an initial range of 2.4%-2.9% to 1.9%-2.4%. US equities initially sold off on the suggestion that the market had not priced-in a slowdown of this magnitude into stocks yet.
The action by the Fed yesterday provided the market with just enough to keep traders from running to the hills. The Fed has left often options on the table in terms of policy action, and should the situation in Europe go supernova, they do have some dry powder left in the form of all-out quantitative easing. With the Fed meeting now having come and gone, the market's glaring eye will now turn back to Europe and the eventual European crisis plan that is expected to come out by the end of the month.