jQuery Cross Domain Ajax Query

I have been quite interested in jQuery nowsday. Before, I use Prototype framework and Scriptaculous framework to do my work. But now, it seems jQuery is more powerful than Prototype. There are conflicts between IE and Prototype framework. I realize some IE on some computer cannot load pages that has loaded Prototype code. I don't know what wrong with that. I try to ask people in the forum, no one can answers this question.

Now, it comes to jQuery 1.2. It includes one of the nicest feature. It allows you to transfer JSON data across multiple domains. Have a look on this:
http://docs.jquery.com/Release:jQuery_1.2/Ajax

jQuery now supports JSONP natively - if you attempt to load JSON (via $.getJSON or $.ajax) from a remote URL then an extra callback will be provided for the server to interpret. Additionally, if the server requires a special field for specifying your own callback name you can provide it by having a "=?" in your query string.