The best place to start and download jQuery is the official web site at http://jquery.com and use the jquery in your file as :
If you’re doing this on a public facing website, you are doing it wrong.
Instead, I urge you to use the Google AJAX Libraries content delivery network to serve jQuery to your users directly from Google’s network of datacenters. Doing so has several advantages over hosting jQuery on your server(s): decreased latency, increased parallelism, and better caching. The jQuery file from google api’s are accessed as :
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js" > </script>