Stock index futures fell on Friday as caution took root following four days of gains, after General Electric Co's quarterly earnings sank and Google Inc pointed to weaker advertising and revenue growth, despite beating expectations.

Bank of America Corp shares dipped after it posted a lower quarterly profit, hurt by a surge in troubled loans as more credit card and mortgage customers fell behind on payments.

Google shares fell more than 3 percent before the opening bell after the weak economy and a slump in advertising spending took a toll on revenue growth and the price of search ads at the Internet company. Its results, posted late Thursday, beat Wall Street expectations.

We've had a big week in the market and there's pressure for some profit-taking, particularly with the weekend coming up, said Joe Heider, president of Dawson Wealth Management in Cleveland, Ohio.

Earnings, combined with profit-taking, are going to be the counter-balancing factors today.

Wall Street capped four days of gains on Thursday, with the S&P 500 <.SPX> posting its best week of the year since early March.

IBM Corp added to the positive sentiment after the closing bell Thursday as the company sharply raised its full-year earnings forecast. IBM shares rose more than 1 percent before the bell on Friday.

Also after the U.S. market's close on Thursday, troubled lender CIT Group said its board of directors and management were evaluating ways to improve liquidity and that the company was in discussions to secure financing.

S&P 500 futures fell 4.4 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 40 points, and Nasdaq 100 futures fell 2.75 points.

Economic data on tap includes housing starts and building permits for June at 8:30 a.m. EDT.

(Editing by Padraic Cassidy)