A street sign for Wall Street hangs in front of the New York Stock ExchangeBy means of Caroline Valetkevitch NEW YORK (Reuters) – The S&P 500 broke a five-day string of document closing highs on Thursday, ending a reasonably unstable session lower as contemporary momentum misplaced steam and Apple shares declined. The Dow also broke its two-day string of all-time closing highs, however still ended above 15,000. The size of the contemporary rally has stunned many investors. Analysts mentioned it's difficult for the upward momentum to continue with out additional catalysts, reminiscent of first-quarter income experiences, which are nearing an end. Extent has been susceptible for far of this year's rally. …