allora l ho provato e funziona, ce un piccolo problema però,

il fade viene esteso anche agli altri elementi contenuti nel div che quindi compaiono e scompaiono.

codice:
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"></script>
<script type="text/javascript" language="JavaScript"> 
			$(document).ready(function(){
				
				var imgArr = new Array( // relative paths of images
					'{T_THEME_PATH}/images/bgheader.gif',
                    '{T_THEME_PATH}/images/bgheader1.gif',
                    '{T_THEME_PATH}/images/bgheader2.gif'
					);
					
				var preloadArr = new Array();
				var i;
				
				/* preload images */
				for(i=0; i < imgArr.length; i++){
					preloadArr[i] = new Image();
					preloadArr[i].src = imgArr[i];
				}
				
				var currImg = 1;
				var intID = setInterval(changeImg, 1000);
				
				function changeImg(){
					$('.headerbar').animate({opacity: 0}, 1000, function(){
						$(this).css('background','url(' + preloadArr[currImg++%preloadArr.length].src +') top center no-repeat');
					}).animate({opacity: 1}, 1000);
				}
 
			});
	</script>


codice:
<div class="headerbar">
        			<div class="inner"><span class="corners-top"><span></span></span>
                    <div style="height: 120px;">
        			<div id="site-description">
        				{SITE_LOGO_IMG}
        				<h1>{SITENAME}</h1>
        				

{SITE_DESCRIPTION}</p>
        				<p class="skiplink">{L_SKIP}</p>
        			</div>
        
        		
        			<div id="search-box">
        				<form action="{U_SEARCH}" method="get" id="search">
        				<fieldset>
        					<input name="keywords" id="keywords" type="text" maxlength="128" title="{L_SEARCH_KEYWORDS}" class="inputbox search" value="{SEARCH_WORDS}{L_SEARCH_MINI}" onclick="if(this.value=='{LA_SEARCH_MINI}')this.value='';" onblur="if(this.value=='')this.value='{LA_SEARCH_MINI}';" /> 
        					<input class="button2" value="{L_SEARCH}" type="submit" />

        					{L_SEARCH_ADV} {S_SEARCH_HIDDEN_FIELDS}
        				</fieldset>
        				</form>
        			</div>
        		
                </div> 
        			<span class="corners-bottom"><span></span></span></div>
        		</div>
sapete aiutarmi??