First you have to find the vistor's country using IP address , for that you can use IP2location database and then you can show the specific information .
You will be required to Geo-Target and first find the IP of your visitor and create a function either in PHP / ASP.Net to divert the user. It would require writing of some code...
What type of site do you have? I managed to find a wordpress plugin that helped me do this on my blog. Only problem is no database is 100% accurate and so some people will get the wrong information (think its normally around 95% accurate)
You can see info on the plugin here Not sure how up2date it is at the moment but I managed to install it and get it working on my site - good luck!