var max = 1;
    var nrImages = 1;
	
    function makeImages() {
		this[0] = "http://unitedteam.com.br/forum/styles/subsilver2/theme/images/banner_001.jpg";
		this.length = nrImages;
    }
	
    var vetImages = new makeImages();
    var x = Math.round(Math.random()*max);
    var y = max / nrImages;
	
    for(var cont = 1;cont*y<= max;cont++) {
		if (x <= (cont*y)) {
			document.write("<img src="+vetImages[cont-1]+" border=0>");
		break;
		}
    }