Investors are famous for their knee-jerk reactions, and today was a perfect example of how spot impressions can lead to big market moves. Throughout much of the day, the Dow Jones Industrials (DJINDICES:^DJI) traded higher, despite some concerning economic data on the manufacturing and jobs front this morning. But, when John Williams, the president of the San Francisco Federal Reserve, said that the Fed could stop its full-out purchase of bonds this summer, and eliminate the quantitative easing program entirely by the end of the year, the stock market got spooked, and the Dow closed down 42 points, while the S&P 500 fell a more substantial half percent.

Within the Dow, a couple of notable decliners were good examples of the dynamics affecting this market. Disney (NYSE:DIS) fell 1.8%, despite its ESPN unit's capturing a lucrative contract for exclusive rights to broadcast the U.S. Open tennis tournament over the next 11 years. Yet, with Disney having hit successive new highs since January, it gets progressively harder for it, and other similarly high-performing stocks, to keep extending their gains to new records.

Meanwhile, Wal-Mart (NYSE:WMT) fell 1.7% after a somewhat disappointing quarterly earnings report. Same-store sales dropped 1.4%, and the retailer cited a reduction in the amount of tax-refund checks it cashed as indicative of the relative weakness of the retail environment during the quarter. A weaker-than-expected forecast for current-quarter earnings also worried investors, despite comments that the company is seeing positive same-store sales trends early on in its fiscal second quarter. Arguably more troubling for long-term investors is the fact that you'd expect Wal-Mart to thrive in challenging economic environments, but that hasn't happened this time around.

Outside the Dow, ReneSola (NYSE:SOL) led the NYSE lower, plunging 13% after it posted a worse-than-expected loss for the first quarter. Although the showing was narrowly better than last year's loss, falling prices and panel shipments for the quarter pushed gross margins negative. Despite the company's assurances that future sales could recover, investors aren't confident about the prospects for ReneSola and many other Chinese solar companies in the current ultra-competitive environment.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool recommends Walt Disney. The Motley Fool owns shares of Walt Disney. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.