Why not just using ajax for Page Requests to load the page content?
ajax, php, request
Solution
Search engines, crawlers/spiders, browsers with no javascript, screen readers and other consumers of the content will not be very happy with it.
You can provide tons of ajax behavior on top of you website if you already support standard server side navigation for the full content. Have a look at progressive enhancement (SO) and progressive enhancement (wiki).
Problem
Many web pages load all of their content to change very little information. Now I would like to know why shouldn't the developers just use ajax for the main page requests? On my own webpage, I would like to develop the main requests on my webpage with just ajax but I don't know any specific cons with this approach. Does anybody have an idea why someone shouldn't use ajax so much?