It will almost certainly use your IP Address to locate the general area of where you live. It is quite a common thing to do these days.
There are many services that can provide this information, a simple Google search returned http://www.ip2location.com/
Taken from this Wikipedia article on Geolocation Software
The primary source for IP address data is the regional Internet registries which allocate and distribute IP addresses amongst organizations located in their respective service regions:
- American Registry for Internet Numbers (ARIN)
- RIPE Network Coordination Centre (RIPE NCC)
- Asia-Pacific Network Information Centre (APNIC)
- Latin American and Caribbean Internet Address Registry (LACNIC)
- African Network Information Centre (AfriNIC)
Secondary sources include:
- Data mining or user-submitted geographic location data. For example, a weather web site might ask visitors for a city name to find their local forecast. Another example would be to pair a user's IP address with the address information in his/her account profile.
- Data contributed by internet service providers.
- Merging databases from different suppliers.
- Guesstimates from adjacent Class C range and/or gleaned from network hops.
Accuracy is improved by:
- Data scrubbing to filter out or identify anomalies.
- Statistical analysis of user submitted data.