* Says doesn't expect significant increase in ad spend next year
* Q3 net loss $5.10/share vs profit 48 cents/share year ago
* Q3 adj EPS $0.26 vs est $0.23
* Q3 revenue $130.3 mln vs est $125 mln
* Sees Q4 revenue $128-$131 mln vs est $128.1 mln
By Melanie Lee
Nov 9 (Reuters) - Sina Corp , the operator of China's largest Internet portal, swung to a third-quarter loss due to hefty writedowns on investments in two online businesses, and said it does not expect a significant increase in advertising spending next year.
China's online advertising market grew 54.9 percent in the third quarter to 13.7 billion yuan ($2.2 billion) with Sina ranking fourth in the overall market behind Google China, Taobao and Baidu , according to Beijing-based consultancy iResearch.
On an earnings call on Wednesday, Sina's management gave a cautious outlook on the advertising market for next year as China's economic growth is expected to cool. Advertising trends are largely tied to macro-economic conditions.
"Overall, the sentiment is good but not great based on our assessment...There may be some increase (in advertising spending) but not significant," Sina's Chief Executive Charles Chao said.
Sina booked non-cash impairment charges -- essentially write-offs of intangible assets -- of $350.1 million in the third quarter due to writedowns on investments in China Real Estate Information Corp (CRIC) and Mecox Lane Ltd .
Shares in loss-making Mecox, an online retailer in which Sina bought a stake in March, have fallen 77.7 percent so far this year, while shares in CRIC, an Internet real estate information and consultancy firm, have fallen around 45 percent.
Excluding one-off items, Sina posted an adjusted profit that beat market expectations helped by strong growth in advertising revenue and user additions on its Weibo platform.
"On the impairment charges, there's really nothing you can do. They've made some bad investments. Mecox Lane was a bad investment for them," said Hong Kong-based Paul Wuh, head of Telecoms and Internet research at Samsung Securities.
Sina shares were down nearly 4 percent in extended trade after closing at $86.94 on Tuesday. They have risen 13 percent this year, compared with a 2 percent fall for the Nasdaq index .
For the fourth quarter, Sina expects revenue of $128-$131 million. Analysts on average expect revenue of $128.1 million, according to Thomson Reuters I/B/E/S.
For the third quarter, Sina posted a loss of $336.3 million, or $5.10 a share, compared with a profit of $31.3 million, or 48 cents a share, a year ago.
The last time it posted a quarterly loss was in the fourth quarter of 2010.
Excluding one-off items, it earned 26 cents a share, beating the average forecast for earnings of 23 cents a share.
Revenue, excluding Sina's separate real-estate advertising business, rose 20 percent to $130.3 million, beating its forecast of $123-$126 million.
Advertising revenue rose 25 percent to $101 million, while non-advertising revenue grew 7 percent.
Sina rolled out specialised Weibo accounts for government officials and a functionality that allows businesses to set up accounts on the platform in the quarter.
Analysts said doubts lingered over when and how the company would monetise its Twitter-like Weibo platform.
Chao said the focus on Weibo is not monetisation but continuing to enhance user experience.
The firm is testing and developing an advertising system for Weibo to be rolled out in the second quarter next year and will continue to enhance its micro-payment platform, he said.
"Our focus now turns to adding more social networking features to Weibo to increase user stickiness," Chao said in a statement.
However, not all analysts agree on the monetisation potential of the user base.
"I'm still cautious for the potential of Weibo right now. This is a social media platform; Twitter is a social media platform that has had problems monetising its platform, that's one of the biggest concerns I have," Samsung Securities' Wuh said. Wuh has a "sell" rating on Sina.
Sina has also faced increasing regulatory scrutiny, with government officials putting pressure on Sina to better police Weibo, which has become a powerful medium to vent frustration against government policies.
Chao said the firm was looking at ways to implement a "better management system" for the platform to counter rumours and "negative sentiment."
"There is no question that Weibo is becoming very influential in China and has become very important in news reporting and public opinion," Chao said, adding that the importance of Weibo has increased government scrutiny.