$.fn.cross = function (intervalo){

	$(this).each(function(a){

		a = $(this);
		
		// *** preparo maqueta  ************************************************************************************************************************************************** // 
	
		anchArea = a.width();
		altoArea = a.height();
		
		a.append("<div class='hover'></div>");
		
		a.children('.hover').width(anchArea);
		a.children('.hover').height(altoArea);
		
		a.children('.hover').css({
			backgroundImage : a.css("background-image"),
			position: "absolute",
			top:0,
			left:0,
			cursor:"pointer"
		});
		
		if($.browser.msie){
		
			a.children('.hover').css({
				backgroundPositionX : "left",
				backgroundPositionY : "bottom"
			});
			
		}else{
			
			a.children('.hover').css("background-position","left bottom");
		}
		
		
		a.children('.hover').css({
			opacity:0,
			zIndex:1
		});
	
		
		if(a.css("position") != "absolute"){
			a.css("position","relative");
		}
		
		a.hover(
			function(){
				
				a.children('.hover').stop().animate({opacity:1},intervalo)
			}
			
			,function(){
				a.children('.hover').stop().animate({opacity:0},intervalo)
			}
		)
	})
}