Stocks gave a mixed showing Wednesday, as the Nasdaq scored a new milestone while the S&P 500 took a breather. The tech-heavy index rose 0.3% for its third straight gain. Intraday, it touched a fresh 14-year high. The S&P 500 lost 0.1%, while the Dow Jones industrial average eased a fraction. Both hit record highs Tuesday. Volume rose across the board in the stock market today from Tuesday’s holiday-impacted levels.