Google Instant is a new real-time search experience which provides results even before you can type and also allows you to quickly view results for autocomplete suggestions.
Google Instant not only provides you with Instant search results, it also provides you with instant autocomplete suggestions to enhance your search experience. Google Instant will be rolled out to users across the world in a phased manner.
If you want to disable or enable Google Instant Search you will need to visit your preference page, and you can turn off Google Instant by clicking the link next to the search box on any search results page, or by visiting your Preferences page.
You can enable the Instant Search by visiting the Preferences page and clicking the link next to the search box again.
Tip: As a temporary solution, if you cannot enable the Google Instant search right now, you can visit http://www.google.com/instant and click on the "Try it Now" button to enable it. You might have to clear cookies in order to disable it later on.