The Fed was forced to do a "rate hike" to save face, though I have to put it in quotes because 0.25% is practically nothing, merely a symbolic gesture so they can say they did it. Probably it will be reversed with suitable "emergency" excuse in short order, or maybe something more subtle like coupling it with QE style injections elsewhere.
Market response will largely depend on whether the hike is perceived as "one and done" or as the start of a trend toward reversion to normal interest rates of several (whole!) percents, which will be a tough trick indeed.
And also, it's an election year so Yellen will want to keep the democrats in power, meaning avoid economic pain during the year, so that's another big reason the rate hike can't really be extended like people seem to expect.