It used to be the case that you could tell what market a stock traded on by the number of letters in its ticker symbol. 3 or less meant the NYSE or AMEX. 4 or more meant NASDAQ. Since 2007 the SEC has allowed NASDAQ companies to trade under one letter and recently Zillow (the web site that allows you to see how much your neighbor's house is worth) has petitioned to use the letter "Z".
LNKD is actually an example of a 4 letter stock trading on the NYSE.