Online publishers have long butted heads with comScore (NSDQ: SCOR) and Nielsen over discrepancies between the publishers’ internal audience-measurement numbers and those issued by the third parties. ComScore announced this morning that it is aiming to address that gap with a new product called Media Metrix 360 that it says provides a more accurate audience figure. The new product blends traditional panel-based information with data from a website’s server. Until now, comScore has relied exclusively on a panel of users as proxy for overall internet use. Critics questioned whether it accurately captured total usage, including on mobile phones and computers used in public places away from the home or office.

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Under the new hybrid service, comScore allows publishers to enable themselves for the server-based part of the system by placing tags on their sites. ComScore has partnered with Akamai (NSDQ: AKAM) to ensure it can handle a large number of requests as publishers initially sign up. Once the tags are embedded on a site, usage can be tracked wherever it is viewed and by whomever is viewing it, not just by the comScore panel. 

The company said it would start measuring audiences in Canada and the U.S. in July, followed by the UK in August, with the rest of the world starting to roll out in the fourth quarter 2009. ComScore will continue to segment results by demographic, geo-demographic and analytic measurements like frequency of use.