Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Chinese map services specialist AutoNavi (Nasdaq: AMAP) lost their way today, falling as much as 12% on relatively heavy trading.

So what: Online media companies in China are dropping like flies today as Internet media generalist SINA (Nasdaq: SINA) fell as far as 8.3% and digital video slinger (NYSE: YOKU) lost 12.8% at worst. AutoNavi shareholders had their nerves tweaked last week with a disappointing quarterly report followed by at least one negative analyst action as Jefferies reduced price and earnings targets while keeping its recommendation to buy -- so it didn't take much to release the tension in a wave of heavy selling.

Now what: After a pretty hot IPO in the summer of 2010, AutoNavi shares have fallen 35% and are setting new all-time lows right now. As if to show that all Chinese Internet stocks aren't the same, (Nasdaq: BIDU) shares have nearly doubled at the same time. AutoNavi stock is fairly cheap by the standards of online media businesses, but analysts are worried about rising operating costs. Keep an eye on the bottom-line margins over the long run, dear Fool.

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Editor's note: A previous version of this article described Jefferies' action as a downgrade. The Fool regrets the error.