Stocks edge higher, but investors remain cautious

Governemnt shutdown continues to affect market

NEW YORK (CNNMoney) -- Investors remained cautious as the government shutdown extended to a fourth day.

The Dow Jones industrial average, the S&P 500 and the Nasdaq edged slightly higher.

The gains come at the end of what's been a mostly down week on Wall Street. The Dow is on track for a 1.5% drop, and the S&P 500 is currently down less than 0.4%. The Nasdaq has managed to hold on to gains for the week.

The government shutdown has created plenty of uncertainty and left an estimated 800,000 federal employees waiting to go back to work.

The shutdown is also delaying the release of the government's monthly jobs report, originally scheduled to come out Friday morning. Since the recession, the report has become the most closely watched indicator on the economy.

With little else to focus on, investors will continue to watch Washington for developments on the budget deal and the looming deadline to raise the debt ceiling. Failure to raise the debt limit is likely to have a significant impact on the global economy, as well as stocks, bonds and currency markets.

Though the political gridlock has sparked volatility on Wall Street, some experts say it is also creating bargains in the stock market.

"Think of this period of uncertainty as a buying opportunity for investors who are under-allocated to equities and have a long time horizon," said Kristina Hooper, head of investment and client strategies at Allianz Global Investors.

What's moving: Shares of Facebook moved modestly higher after the company said it will start selling advertising on its photo sharing tool Instagram.

Facebook competitor Twitter made its IPO filing public late Thursday. Twitter revealed that it is still unprofitable. The company also said it will trade under the symbol TWTR, though it hasn't yet said on which exchange it will list. Goldman Sachs is the lead underwriter for the IPO.

Though Twitter's IPO is the most highly anticipated market debut since Facebook, investors were salivating over the IPO of a Chicago-based sandwich shop Friday. Potbelly surged more than 120% from its offering price as it began trading on the Nasdaq.

Adobe shares were lower after the company said that hackers had accessed personal data for nearly 3 million of its customers.

Tesla shares were modestly higher following a three-day slide that shaved more than 10% of the value off the electric car maker's high-flying stock.

European markets edged higher in afternoon trading, led by France's CAC 40.

The major Asian markets ended with losses. The Nikkei shed nearly 1% after the Bank of Japan wrapped up its two-day monetary policy meeting and opted to maintain its stimulus measures. South Korean electronics manufacturer Samsung said it was on track for another record quarterly profit.

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