var header =
{
	tid : 0 ,
	
	imgurl:function(id)
	{
		switch(id)
		{
			case 'menu-home':
				return "images/uni2.jpg" ;
			case 'menu-intro':
				return "images/uni.jpg" ;
			default:
				return 0 ;
		} 
	},
	
	change:function(id)
	{
		// get image url from id
		var url = header.imgurl(id) ;
		if(!url) return ;
		var fadetime = 1000 ;
		var imag = $("#header > img") ;
		// repeated image : if header image is current showing no need to fade again
		if(imag.attr("src") == url ) return ;
		// if another fading exists clear it first before new fadein
		clearTimeout(header.tid) ;
		// fadeout previous image
		imag.fadeTo(fadetime,0) ;
		header.tid = setTimeout(function(){
	 		imag.attr("src",url );
			imag.fadeTo(fadetime,1);
		},fadetime) ;
	},
	init:function()
	{
		var mitem = $(".item,.item2") ;
		mitem.mouseover( function(){
			//alert("mouseover") ;
			header.change($(this).attr("id")) ; 
		});
	}
	
}