How can we change only inner part of a web page?

Question

I am developing a web application, where headers and footers for all pages are the same. What I want to achieve, is to change only the part of the page between the header an

Answer 1

You are looking for AJAX (acronym for Asynchronous JavaScript and XML)

in jQuery you can use $.ajax

here is an example/tutorial on how to do this with php.