I noticed that jquery\'s beta template plugin is using, the type attribute \"text/x-jquery-tmpl\"
e.g
The type actually does indicate what sort of script is there. If the browser doesn't understand it, it should ignore it. In this case, it's a convenient and semantic sort of way to include the source of the template without displaying it on the screen.
Usually with jquery template, you'll give it an id and refer to it that way with your $(id).tmpl call.
script def here: http://www.w3.org/TR/html401/interact/scripts.html#idx-scripting_language
examples of tmpl here: http://api.jquery.com/tmpl/
No, MIME are provided by the server to identify resources. The browser then acts on the types it recognizes.
Yes, in the HTTP connection the browser lists the types it can recognize so the server can choose types that fit better (an example here would be HTML 5 and video, where you have some codec options and the browser may support only a subset).
In this case, the specific MIME helps to signal the browser a warning: "This is not normal Javascript, don't act on it like if it was."