When Web-analytics provider StatCounter reported that Microsoft's (NASDAQ:MSFT) Bing yielded market share to Google (NASDAQ:GOOG) last month, it led me to ponder some questions.

Are searchers tiring of Bing now that the novelty has worn thin? Did the deal to power Yahoo!'s (NASDAQ:YHOO) searches make Microsoft the evil meanie again? And is this reliable data, or do we wait for larger trackers such as Hitwise to report?

Well, the first two questions are still debatable, but Experian's Hitwise unit has now checked in with its search-engine metrics for September. If Bing was looking forward to a second opinion, it's not going to like what Hitwise has to say.

Company

August

September

Change

Google

70.24%

71.08%

1%

Yahoo!

16.96%

16.38%

(3%)

Microsoft

9.48%

8.96%

(5%)

Ask.com

2.37%

2.56%

8%

Source: Experian Hitwise.

The numbers don't line up exactly the way they did in the StatCounter report, but the end result is the same. Google gained market share last month at the expense of Yahoo! and Microsoft. IAC's (NASDAQ:IACI) Ask.com also gained ground, but it remains a distant fourth-place finisher.

The heat is on at Bing. Now that two independent analytics specialists are confirming that Bing is slipping -- for the first time since its springtime launch -- Microsoft needs to stop a further slide.

Its first wave of "decision engine" ads were effective, if annoying. Now Microsoft needs to pick up the tempo, even if it means calling out Google by name.

There's nothing wrong with calling out the market leaders. It has certainly worked for Apple (NASDAQ:AAPL) as it makes a dent in the Windows-powered stronghold with its "I'm a Mac, I'm a PC" ads. Now it's time for Microsoft to turn the tables on Google, just as it has on Apple in positioning its Zune against the iPod.

It may also be time to take charge of emphasizing its shopping tab and cash-back rebate offers as we head into the holiday shopping season, just as Ask.com has done with this week's Ask Deals makeover.

Microsoft can't stand still. One monthly slip is a blip or an anomaly. Back-to-back monthly slips would be a trend.

Did Bing peak in August, or is there hope for Microsoft's search engine? What do you think? Let us know in the comment box below.

Google is a Motley Fool Rule Breakers recommendations. Microsoft is a Motley Fool Inside Value pick. Apple is a Motley Fool Stock Advisor selection. Try any of our Foolish newsletter services free for 30 days.

Longtime Fool contributor Rick Munarriz wonders whether we'll even be using search engines 10 years from now. He owns no shares in any of the stocks in this story and is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.