Stock futures indicated a higher start earlier this morning following solid results from internet bellwether Yahoo late Tuesday. As earnings reports have started coming out this morning, though, stock futures have started to reverse direction.

Other than many earnings reports on tap today, investors may look at U.S. oil inventories when out later today after reaching nearly $120 a barrel (10 cents shy) Tuesday. Analysts expect supplies declined in the past week. So far oil has moved somewhat lower today, but remained near $118 a barrel.

U.S. stocks tumbled Tuesday following some disappointing results from several tech and consumer stocks. The Dow industrials dropped 104 points, or 0.82%, the S&P 500 fell 12 points, or 0.88%, and the Nasdaq Composite lost 31 points, or 1.29%.

Despite many upcoming earnings reports, investors will likely continue to focus on Yahoo! (NASDAQ: YHOO), which has reported strong results, beating analyst estimates on both the top line and bottom line. Still, the results weren't phenomenal, or uncovered any surprising issue that might show it could fare better on its own. Yahoo! has until Saturday to accept Microsoft (NASDAQ: MSFT)'s takeover offer of $31 a share or face a proxy fight. Microsoft has already said it wouldn't raise its offer, but of course, nothing is certain at the moment. YHOO shares are down about 0.8% in premarket trading.

Reporting today are Boeing (NYSE: BA), Delta (NYSE: DAL), GlaxoSmithKline (NYSE: GSK), Anheuser Busch (NYSE: BUD) and UPS (NYSE: UPS) before the markets open.

After the close, Apple (NASDAQ: AAPL) and Amazon.com (NASDAQ: AMZN) are scheduled to post results.

Ambac (NYSE: ABK), the second-largest bond insurer which has captured may headlines lately following record losses and threats from credit companies to trim its ratings, posted a wider loss -- an operating loss of $6.93 a share -- than analysts estimated ($1.82 per share) after taking $3.1 billion in charges for subprime-mortgage securities. ABK shares are down about 8.8% in premarket trading.