Is there a way to change the browser's address bar without refreshing the page?

Question

With HTML5 you can modify the url without reloading:

If you want to make a new post in the browser's history (i.e. back button will work)

window.history.pushState('Object', 'Title', '/new-url');

If you just want to change the url without being able to go back

window.history.replaceState('Object', 'Title', '/another-new-url');

The object can be used for ajax navigation:

window.history.pushState({ id: 35 }, 'Viewing item #35', '/item/35');

window.onpopstate = function (e) {
  var id = e.state.id;
  load_item(id);
};

Read more here: http://www.w3.org/TR/html5-author/history.html

A fallback sollution: https://github.com/browserstate/history.js

To add to what the guys have already said edit the window.location.hash property to match the URL you want in your onclick function.

window.location.hash = 'category-name'; // address bar would become http://example.com/#category-name

I believe directly manipulating the address bar to a completely different url without moving to that url isn't allowed for security reasons, if you are happy with it being

www.mysite.com/products/#{selectedCat}

i.e. an anchor style link within the same page then look into the various history/"back button" scripts that are now present in most javascript libraries.

The mention of update panel leads me to guess you are using asp.net, in that case the asp.net ajax history control is a good place to start

I don't think this is possible (at least changing to a totally different address), as it would be an unintuitive misuse of the address bar, and could promote phishing attacks.