The Web metrics firm Net Applications issued its first survey of the mobile search market overnight Sunday, and Apple’s (AAPL) iPhone emerged with what the report describes as a “commanding lead.” (link)

As Net Applications measures it — a big caveat (see below) —  nearly 2/3 of  Web searches conducted on a mobile device in the month of February were made from an iPhone.

The other contenders had only thin slices of the mobile Web search pie — although according to this analysis, Android and BlackBerry are rapidly gaining market share.

“This does not mean that iPhone web browsing is shrinking,” the report notes, “because the overall market is growing rapidly.” (link)

Google’s (GOOG) Android is singled out for having grabbed more than 6% of mobile web browsing in less than five months. Others came in with comparable shares — Microsoft’s (MSFT) Windows Mobile had 6.91% and Nokia’s (NOK) Symbian 6.15% —  but they’ve been around much longer. The stongest contender among the also-rans with 9.1% was an OS you don’t hear much about: Java ME, a subset of Sun Microsystems’ (JAVA) Java platform popular among developers for creating games and other applications for cell phones.

Research in Motion’s (RIMM) BlackBerry share in this survey is so small it is consigned to the catch-all “other” category.

How can this be, given that there are a lot more BlackBerrys out there than iPhones?

Part of the answer is that it’s easier to surf the Web on an iPhone. But a more important reason emerges from Net Applications’ description of how the survey was conducted:

“Our mobile share methodology measures share for browser capable mobile devices. This means the mobile device must be able to render HTML pages and javascript.  Visits to WAP pages are not included.” (link)

WAP (for Wireless Application Protocol) was the Web browsing standard for BlackBerries and other mobile phones  —  famously dismissed by Steve Jobs as the “baby Web”  — until the iPhone came along and offered a Web browser with HTML and Javascript.

In other words, Net Applications is judging the race for mobile Web dominance using the rules set by the iPhone.

Net Applications’ monthly surveys have long been controversial. Although the firm has  a fairly large data base — it samples browser data from more than 160 million monthly visits to websites operated by its clients — it describes the results as “market shares,” a term usually reserved for share of market as measured by revenue or unit sales.

But Net Applications does provide a consistent methodology by which to gauge browser and operating system trends. (See Ars Technica’s “Making sense of Mac market share figures,” published just last week.)

Net Applications’ mobile browser report is available here.

Preliminary results from the same survey show a small drop in Mac OS X’s Internet share. But that’s another story. See Apple’s Net share slipped in February.