For the first issue you can control the location open up the about:config page. In order to change your Firefox Configuration please do the following steps :

1. In the Location bar, type about:config and press Enter. The about:config "This might void your warranty!" warning page may appear.
2. Click I'll be careful, I promise! to continue to the about:config page.
3. Locate the preference geo.enabled, double-click on it to change its value to false

In order to turn off the second setting you can find the option in this menu:

• Firefox > Options/Preferences > Advanced > General : Accessibility : [ ] "Warn me when web sites try to redirect or reload the page"

"... user's tentative location."

As mentioned above the GeoLocation feature is uses Wi-Fi location data - like the WiFi router location and its proximity to other WiFi routers, and can determine an exact street address of the "location". But Firefox users will be asked every time a website wants to "use" the GeoLocation to determine your location. And that can be turned off entirely, as mentioned above by my esteemed colleague.

Many websites determine "location" based upon the IP Adresss of the connection being used, which might be accurate to (say) a 4 block radius or maybe only the community you are connecting to the internet from - depending upon the Internet Service Provider. Over the last 15 years of using the same broadband Cable ISP, I have seen my reported "location" get more "exact" as far as my physical location is concerned. 15 years ago I was shown one community over - 5 miles by "line of site", but now my location is more pinpointed to an intersection where my cable company has major connection "box" for the surrounding neighborhoods - just 3 blocks from my real location. Non-urban areas are nowhere near as accurate - posts have been made here by users living in northern WA state who were connected via a Canadian cable company even though they were paying a US company for internet service. If going over the border to connect a customer is the cheapest way to "connect" - an ISP will do that to save costs.. Although it does make internet users ask why they are getting CA search results when they reside in the USA. To "disable" that, something along the lines of using a proxy would be needed to make you more "anonymous" as to your reported physical location.

Oh, and like anything else involving computers and the internet there are different "sources" for the "location" information - both WiFi and IP Address. And that information may not always match what another "source" reports. I'm not sure how IP Addresses are determined, but the various browsers do use different sources for GeoLocation / WiFi data.