It's difficult to sort out tracking mobile media site hits if no one can even agree on how to do it with regular Web sites.

The New York Times reports that while the Web has ushered in a new era of audience measurement, allowing for far greater accuracy than traditional magazine readership and TV audience estimates, there's still a lot of disagreement on exactly what constitutes a unique visitor, a site hit, and an ad impression.

This becomes evident when comparing a site's internal measurements -- Style.com reported 1.8 million visitors last month -- versus external audience tracking -- ComScore reported 427,000 visitors to Style.com, while Nielsen/NetRatings claimed 497,000. This discrepancy has a profound effect on advertising rates, and is preventing Web advertising from growing further, according to the Times article.

How Many Site Hits? Depends Who’s Counting [NYT]