Google’s Geolocation API allows developers to pinpoint your computer’s location by looking at the WiFi networks around you,Chrome has had geolocation support since March, but it wasn’t activated by default until now. The support hasn’t yet arrived in the beta or stable versions of Chrome.
For now, this new feature is still hidden behind a command line toggle and only available in the developer builds for Windows and OSX Leopard (it doesn’t work on Snow Leopard yet).
If you want to use geolocation for now in Firefox or Chrome , then one way is to go to Google Maps and click the small white circle in the upper-left corner of a map itself, below the navigation control and above the zoom control. A pop-up bar says, "http://maps.google.com/ wants to track your physical location," and if you click "allow," your location should then be shown with a blue circle on the map.
The Chrome team also notes that the geolocation UI is still incomplete and that Chrome will forget the permissions you set.