Change the URL in your HTML from
// instead of
https:// is a shorthand -- supported by all major browsers -- which means "the same protocol as the parent page is using". In other words, if your own site uses SSL, then jQuery will be served over SSL. If not, then your users will use plain HTTP for jQuery, and benefit from the faster connection setup un-encrypted HTTP has.
When serving content with a full version number -- the
1.6.0 part -- Google's CDN will automatically use long caching headers. The URL you used means "the newest in the 1.6 series", and is served with shorter caching headers, so that Google can quickly update when jQuery releases a new version.
You can verify that this works with Rex Swain's HTTP Viewer if you'd like. (NB: this HTTP viewer doesn't support the
// shorthand, but browsers do.)