Load script asynchronously

In a text widget, I have put some JS to load a content piece from another website.

How can I make this widget (or at least the JS) load asynchronously? Also, I’d like to set a timeout, in case this other site is slow or offline.

In case you are curious, the JS in the text widget looks something like this:

<script type="text/javascript" src="http://www.domain.com/javascript/jquery/jquery-1.6.1.min.js"></script>
<script src="http://www.domain.com/javascript/jquery/jquery.bxSlider.min.js"></script>
<script src="http://www.domain.com/javascript/jquery/jquery.easing.1.3.js"></script>
<link rel="stylesheet" href="http://www.domain.com/stylesheet.css"/>
<script  src="http://www.domain.com/getwidgetscript&widget_type=content_tb&show_description=1&show_type=horizontal&show_once_quantity=1&products_limit=20&categories=37"></script>