Serving images based on where people are viewing it?

I would like to serve different background images based on a) where people are coming from (USA, UK, Australia) and b) whether it is day or night.

Is it possible doing this using only frontend technologies (I ha开发者_JS百科ve complete access to the html, not to the actual app's backend though?).

You can use the local time of the client to determine wether it is day or night

and have a look here, there is a javascript example of how to get your location.

http://merged.ca/iphone/html5-geolocation