Google - how do they do that?

Not the search queries.

But the way the web page updates, when you type a key?

Do you mean the search suggestions?

It uses a technique called AJAX.

There's some Javascript in the web page. When you type a key this triggers an event and the browser "posts" to the server in the background.

Then the auto-suggestion list is retrieved based on what you typed in so far, and the screen is updated dynamically without the need to reload the entire page.

If you happen to mean Instant Search, this may help:

Google Blog

You can by the way turn the facility off

I do shudder to think how much money they have ploughed into their infrastructure to support it - we count our visits in millions per week and it makes us wince to think about it

In reply to a post by MarkHampshire:

and the screen is updated dynamically without the need to reload the entire page.

Is that part of AJAX?

AJAX is a method of using live data rather than a specific language set.

A PHP/JavaScript example can be found here

You can use any combo of languages to get the desired effect, PHP/JavaScript being the most popular.

OK - Thanks.

I have the idea of how it works now.

Just noticed - The google app only works on Firefox - and not on IE.

Google Instant may not work properly, if you have a slower Internet connection.
But it works perfectly on average broadband connections.

I think they now turn it off on slow connections.