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 Cheetah Mobile (NYSE:CMCM) fell 16% Tuesday after the Chinese Internet security software specialist released unaudited first-quarter results.

So what: Quarterly revenue jumped 131.6% year-over-year to $50.8 million, which translated to a 4.8% decrease in adjusted net income to $5.3 million, or $0.04 per diluted American depositary share. In addition, Cheetah Mobile sees second quarter revenue between RMB335 million and RMB345 million. Based on today's exchange rates, that's between $53.9 million and $55.5 million, or an increase of 111% to 117% from the same year-ago period.

Now what: There are currently no analyst estimates to compare, but Cheetah Mobile only just held its IPO three weeks ago and is prone to plenty of volatility right now. But given the decelerating growth indicated by Cheetah Mobile's second-quarter revenue guidance, investors should keep their eyes on whether Cheetah Mobile's outsized top line increases are sustainable over the long term.

In addition, with regard to Cheetah's falling profitability, first-quarter operating expenses jumped 148.8% over the same period last year. Cheetah Mobile states this was "primarily due to an increase in research and development expenses, selling and marketing expenses, and general and administrative expenses" -- or, in other words, essentially every one of its expense categories.

In the end, with its shares currently trading at a rich 20 and 169 times trailing 12-month sales and earnings, respectively, I'm perfectly happy watching this one from the sidelines.