Source: Baidu. 

We will get another snapshot of China's Internet market when Baidu (NASDAQ:BIDU) reports after Wednesday's market close. 

China's leading online search engine will let us know how it wrapped up 2014, and the market's holding out for healthy top-line growth. Analysts see revenue of $2.26 billion, soaring 48% since the prior year's fourth quarter. That's pretty impressive when pitted against the global leader that's growing at less than half that clip, but this doesn't mean that Baidu's at its best right now.

Investors were pumped when revenue growth began to accelerate at Baidu in 2013, but it's now starting to slow down. Revenue posted a 52% year-over-year pop last time out

The bigger concern at Baidu is its bottom line. The dot-com giant may have beaten analyst profit targets by a double-digit percentage margin in each of the past three quarters, but profit margins have been contracting. Baidu -- like other Chinese Internet rock stars -- has been expanding into areas that don't pack the same kind of margins as its flagship search business. Analysts see earnings per share climbing 27%. That's not too shabby in and of itself, but it translates into another period of net margins going the wrong way.

Margins have come down a long way. Baidu's net margins peaked at 47% in 2012, according to S&P Capital IQ data, before falling to 33% in 2013 and dropping below 30% through the first three quarters of 2014. It's not easy to turn a fat profit running popular mobile app marketplaces and a streaming video portal.

The mobile revolution has also been a mixed blessing. As most Internet companies have found out lately, ads and paid search on mobile devices aren't as lucrative as on traditional PCs. Baidu announced during the third quarter that it's seeing more traffic on mobile than PC devices for the first time. That's welcome news to silence the naysayers that felt Baidu would lose its pole position as China goes mobile, but there's also a price to pay: mobile accounted for just 36% of Baidu's revenue during the quarter.

Investors will want to see mobile monetization improve, of course, but nothing would give the stock a bigger shot in the arm than improving its margins. The market's resigned to the contraction, but has been willing to accept it for the sake of heady overall growth. If we look out to 2015 we see analysts targeting revenue and earnings-per-share growth of 41% and 36%, respectively. Yes, that once again suggests that margins are contracting, but you won't find too many people complaining about a dot-com speedster growing its bottom line at a 36% clip. That finds Baidu trading at just 25 times this new year's projected profitability, and that's a multiple that could prove to be even lower if it lives up to its recent streak of blowing through analyst income forecasts.

Given the many moving parts at Baidu these days there are plenty of factors that could move its report and influence its guidance. The stock may have more than doubled over the past two years, but as it's trading slightly lower so far in 2015 it won't be a surprise if Wednesday afternoon's report moves the stock.