This jQuery ajax upload plugin creates a hidden iframe and sets the form's target attribute to post to that iframe. When the form is submitted, it is posted (including the file uploads) to the hidden iframe. Finally, the plugin collects the server's response from the iframe.
This latest version includes a major bug fix and has a couple of new features.
For documentation and examples on how to use this plugin, or to get in contact with me visit
http://www.jainaewen.com/files/javascript/jquery/iframe-post-form.html