not sure what you are asking specifically.
a "site" can't do a redirect based on geography.
a server or a script can respond to a request by detecting language preferences in a browser, ip address of requesting user agent/proxy or a cookie indicating a previous preference setting and redirect accordingly.
you can also make some guesses based on referrer, such as referred search traffic from google.co.uk vs google.com.
is that what you are asking about?

I got these answers in response to my my questions:-

"A server or a script can respond to a request by detecting language preferences in a browser, ip address of requesting user agent/proxy or a cookie indicating a previous preference setting and redirect accordingly."

but i still want to know,

1.) How to put the the script on websites?
2.) Does it affect the Search Engine Rankings, if yes how?
3.) How it effects tracking of visitors?

1.) How to put the the script on websites?

As per the above, this would be something you do with your server, not the website per se.

2.) Does it affect the Search Engine Rankings, if yes how?

That would depend on what you implemented and how.

3.) How it effects tracking of visitors?

That would depend on what you use for tracking and #2 above.

>>1.) How to put the the script on websites?

it's not straightforward, you would need a database of ip addresses mapped to locations as a minimum i should think, these you can buy or i believe there are some free ones available.
you will then need to code the logic - what you want to do with the different geo locations
as far as i know there is no off the shelf product that will do what you are looking for, so it is not trivial to impliment

>>2.) Does it affect the Search Engine Rankings, if yes how?

you should serve search engine spiders the appropriate geo located pages from where they come from

it is possible to do some of this with server directives.
for example you can use the apache mod_rewrite module to redirect based on referer or ip address or cookie value but it would be difficult to implement a comprehensive solution this way.
you can use mod_negotiation to provide content selection based on user agent language preferences, but this may not be a preferred solution since several variants of the content may be served to the same requested url (although there will be a Vary HTTP response header returned with additional information.)
you would probably want to direct your request to a script that examines the request responds appropriately.
the resulting response has so many variables that you couldn't possibly answer your questions about ranking and tracking until you know more implementation specifics.