Can You Please Explain your Actual requirement ...
there Can be Some Caching issues in your case (am not sure) ..
on server side you have to make sure that you wont cache a response
use this to enabling no-caching
i Guess you are using HTTP GET method . if you use it you may be getting same response ...
if you are using POST you have to do some tuning on XMLHttpRequest check this link Ajax POST
check these also ajax link