Javascript Example
Screen shot
Change Background Color of the webpage

<html>
<head>
<title>Change Back Ground Color of the Webpage</title>
<script language="javascript" type="text/javascript">
function change_color(value)
{

if(document.getElementById("red").value==value)
{
document.bgColor="red";
document.getElementById("green").checked=false;
document.getElementById("blue").checked=false;
}

if(document.getElementById("green").value==value)
{
document.bgColor="green";
document.getElementById("red").checked=false;
document.getElementById("blue").checked=false;
}

if(document.getElementById("blue").value==value)
{
document.bgColor="blue";
document.getElementById("red").checked=false;
document.getElementById("green").checked=false;
}

}
</script>
</head>
<body>
<h3>Click on Checkbox to change color of the webpage</h3>
<input id="red" value="red" type="checkbox" onClick="change_color(this.value);"/>Red <br>
<input id="green" value="green" type="checkbox" onClick="change_color(this.value);"/>Green <br>
<input id="blue" value="blue" type="checkbox" onClick="change_color(this.value);"/>Blue <br>
</body>
</html>

You can download source code here