What happened?
China's economy might not be as robust as it once was, but some of its biggest companies are still reporting solid growth. Such is the case with web giant SINA Corporation (NASDAQ:SINA), which posted a fiscal Q4 2015 that exceeded analyst expectations.

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For the quarter, the company's net revenue was $256 million, 21% higher on a year-over-year basis. The bulk of this amount consisted of advertising revenue that increased 23% to $223 million. Adjusted attributable net income came in at just under $25 million ($0.35 per share).

Both the top and bottom lines topped the average analyst estimates, which anticipated $242 million and $0.33 per share, respectively.

For the entirety of fiscal 2015, net revenues improved by 15% over 2014 to $881 million, while adjusted attributable net income landed at $56 million, against the previous year's $52 million.

In addition, the company's board of directors approved a fresh stock buyback plan, for up to $500 million worth of shares. The authorization expires at the end of June 2017.

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Does it matter?
There's one big reason for SINA's nice improvements in the top and bottom lines -- Weibo (NASDAQ:WB). The microblogging site (more or less China's equivalent of Twitter) was spun off from SINA in a 2014 IPO; the former parent still has a majority stake in the company.

That was a good thing, too, at least for this past quarter. Weibo's advertising revenue rose during its Q4 -- by 47% to nearly $130 million -- while the collective take from SINA's other businesses was basically flat.

As Weibo goes, so goes SINA. The former turned in current-quarter revenue guidance that indicates it might not top the $115.4 million estimated by analysts. Somewhat mirroring that tepid projection, SINA's guiding for revenue of $850 million to $950 million for the entirety of 2016; the market is expecting $985 million.

Even at the upper range of that projection, the top line would grow 8% -- not bad, but certainly not the model of a hot Internet company. That'll probably keep the stock price down, despite those new buybacks.

Eric Volkman has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Twitter, and recommends Sina. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.