First of all you can do a whois on an IP address to get where the company that registered is located. If you traceroute the address you can sometimes get hints

First of all you can do a whois on an IP address to get where the company that registered is located. If you traceroute the address you can sometimes get hints on where it is. And then some big sites may use geo locotation services on their websites that query the browser/APP GPS where the user is located and then it may be concluded that the whole /24 net is within that area and then the site will sell this information to geo location services.