function message(text, bol_error) {
	var theBody = document.getElementsByTagName("body")[0];
	var theNode = document.createElement('div');
	var left = (screen.width/2)-250;
	var top = (screen.height/2);
	theNode.style.position = 'absolute';
	theNode.style.top = top+'px';
	theNode.style.left = left+'px';
	theNode.style.width = '300px';
	theNode.style.padding = '50px';
	theNode.style.textAlign = 'center';
	theNode.style.borderRadius = '1em';
	theNode.style.MozBorderRadius = '1em';
	theNode.style.fontSize = 'medium';
	theNode.style.opacity = 0.0;
	theNode.style.MozOpacity = 0.0;
	theNode.style.KhtmlOpacity = 0.0;
	theNode.style.filter = "alpha(opacity=100)";
	theNode.style.backgroundColor = (bol_error)? "#FFA1A1":"#F5F5F5";
	theNode.style.backgroundImage = 'url('+mxClient.imageBasePath+'/messagebox_warning.png)';
	theNode.style.backgroundPosition = '5px 5px';
	theNode.style.backgroundRepeat = 'no-repeat';
	theNode.style.border = '2px dashed #A6A6A6';
	theNode.style.display = "block";
	theNode.style.zIndex = '100';
	theNode.innerHTML = text;
	theBody.appendChild(theNode);
	fade('in',theNode,1000);
	setTimeout( function(){fade("out",theNode,2000)}, 3000);
	setTimeout( function(){theBody.removeChild(theNode)}, 6000);
}

function fade(direction, elem, time) {
	if (typeof elem == 'undefined') return;
	(function go() {
		if(direction == 'in') {
			elem.style.opacity = parseFloat(elem.style.opacity)+0.1/time*1000;
			elem.style.MozOpacity = parseFloat(elem.style.opacity)+0.1/time*1000;
			elem.style.KhtmlOpacity = parseFloat(elem.style.opacity)+0.1/time*1000;
			// for IE
			elem.style.filter = 'alpha(opacity=' + elem.style.opacity * 100 + ')';

			if( elem.style.opacity < 1 ) {
				setTimeout( go, 100 );
			} else return;
		} else {
			elem.style.opacity = parseFloat(elem.style.opacity)-0.1/time*1000;
			elem.style.MozOpacity = parseFloat(elem.style.opacity)-0.1/time*1000;
			elem.style.KhtmlOpacity = parseFloat(elem.style.opacity)-0.1/time*1000;
			// for IE
			elem.style.filter = 'alpha(opacity=' + elem.style.opacity * 100 + ')';

			if( elem.style.opacity > 0 ) {
				setTimeout( go, 100 );
			} else return;
		}
	})();
}

shows a messagebox (better alert) with fade effekt

message fade-in/out

JavaScript