Look at the domain. If I'm downloading jQuery, it should be jquery.com. If I'm not sure what the domain should be, try to get it from someone I do trust, like t

Look at the domain. If I'm downloading jQuery, it should be jquery.com. If I'm not sure what the domain should be, try to get it from someone I do trust, like the Google-hosted libraries[1]. If it's from GitHub or BitBucket, try to make sure the person who owns the repo is actually the one maintaining it (so I don't get a broken copy or one with something "extra"). It's all mostly just common sense and a little bit of extra scrutiny. [1] http://code.google.com/apis/libraries/devguide.html http://code.google.com/apis/libraries/devguide.html