Most menu software developers would say that their menu software supports menu fading. However, they do not truly support cross-browser compatible fading; they support Internet Explorer's proprietary methods, which doesn't take any effort to implement anyway.
WebDDM supports truly cross-browser compatible fading; Fading works in Mozilla 1.5 and up (and all browsers based on Mozilla such as FireFox, Galeon, and K-Meleon), Safari 1.1 up, and Internet Explorer 4.0 and up. To make this transition work, you must include one JavaScript libary found in the js/ directory. As of WebDDM 3.4, fading menus are no longer core to WebDDM - it is a plugin. However, implmentation is exactly the same on your side. Your code should look something like this if you need to use this transition:

<script src="../js/core.WebDDM.compressed.js"></script>
<script src="../js/alphaTrans.WebDDM.compressed.js"><!-- For fading transitions --></script>

Fading is another feature that is almost insultingly easy to use in WebDDM.
Fading is defined on a per-item-container basis; you define it for the item container (the 'items' array) and all items fade equally.

'items':{
	/* Fade controls */
	'alphaTrans':{
		'maxOpacity':100, // Maximum opacity, 0-100
		'delta':1, // Change in opacity per update
		'delay':10, // Delay between changing opacity
		'inDelay':10, // Optional if delay is set; delay for fading in
		'outDelay':50, // Optional if delay is set; delay for fading in
		'direction':'both' // Direction of fading: in,out,both
	},
	// Extra code here....
}

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