So if you are using a piece of code like the following:
consider using the Google AJAX Libraries like this instead:
Doing so, you are reaping 4 benefits (decreased latency, increased parallelism, better caching and less traffic) from it:
By using the CDN (Content Delivery Network) of google you make sure that the visitor downloads the script from the closed available server belonging to google. Therefore the download might be faster and the response time shorter.
Probably the greatest benefit of using a CDN like e.g. the Google AJAX Libraries is that your visitors may not need to download jQuery at all even on the first visit. If the visitor have ever surfed an website also using the Google AJAX Libraries, it’s highly likely that it’s already in the browsers cache. This is also a big benefit for the user, since he/she doesn’t need to have dozens of identical copies of jQuery in their browser’s cache. Also the caching is optimally configured and browser can cache the file for up to one year.
For smaller websites another benefits might be that less of the valuable traffic is actually send on sending “website internals” to the visitor. Nothing send, nothing paid.