imgArray = new Array('img1');

var i = Math.floor(Math.random() * imgArray.length);

function imgLoad() {
    document.writeln('<style type="text/css"> <!-- #indeximage {background: url(images/index/' + imgArray[i] + '.jpg); background-repeat: no-repeat; width: 700px; height: 500px; padding-left: 30px; padding-top: 20px;} --> </style>');
}