$(document.body).append($(document.createElement('script')).attr({
  type: 'text/javascript',
  src: 'http://localhost/json.js'
}));

The code above creates a script element, sets attributes and appends it to document using jQuery dom manipulation.

In my IE7, two requests are sent to server.

It turns out that IE7 sends the request right after you set the src attribute even if the script element is not attached to the document tree yet. Then jquery calls evalScript in append, making another request.

Though this is technically not a jQuery bug, it could cause hard to find bugs.