If you host a web site, or if you host a web site for someone else, download your own JQuery library (or other library for that matter).
JQuery, for example, uses a CDN for web sites that want to link to a hosted Jquery.
You can find that information here:
Here’s the actual file:
Personal preference, host your own. That way, no one can change it without you knowing, and therefore breaking your web site.
Please, for super serious, don’t link to an unknown site that shows up on the 5th page of Google. That’s how you start to host malware.