var rimages = new Array();
rimages[0] = "images/random0.jpg";
rimages[1] = "images/random1.jpg";
rimages[2] = "images/random2.jpg";
rimages[3] = "images/random3.jpg";

function grabImage() {
	document.write("<img src='" + rimages[Math.round(Math.random()*3)] + "' border='1' alt='' />");
}