function image() {
};

image = new image();
number = 0;

image[number++] = "<img src='images/1.jpg' alt='Redkite Internet' border='0'>"
image[number++] = "<img src='images/2.jpg' alt='Redkite Internet' border='0'>"
image[number++] = "<img src='images/3.jpg' alt='Redkite Internet' border='0'>"
image[number++] = "<img src='images/4.jpg' alt='Redkite Internet' border='0'>"

increment = Math.floor(Math.random() * number);

document.write(image[increment]);