HTML5 Geolocation API: Your Browser Knows Where You Are

One of the pieces of functionality commonly discussed when distinguishing HTML5 from previous versions of HTML is the standardization of geolocation via the Geolocation API. Although some browsers supported geolocation functionality prior to HTML5, it is the standardized API that brings new value. This is true of many aspects of HTML5 where HTML5 standardizes across compliant browsers what formerly required browser-specific extensions. The geolocation standardization process is not technically part of the HTML5 specification [it is its own World Wide Web Consortium(W3C) specification], but its timing makes it easy to lump in with other HTML5 enhancements. In other words, it is “HTML5″ in the larger sense of “next generation HTML” as opposed to strict HTML5 as outlined in the specification.

Read more here