Javascript Example
Screen shot
Javascript CheckBox Validation

<html>
<head>
<title>Javascript Example</title>
<script language="javascript" type="text/javascript">
function validate()
{
var str=true;

document.getElementById("msg").innerHTML="";

if(document.frm.hobby1.checked || document.frm.hobby2.checked || document.frm.hobby3.checked || document.frm.hobby4.checked)
{
str=true;
}
else
{
document.getElementById("msg").innerHTML="Please select any one";
str=false;
}

return str;

}
</script>
</head>

<body>
<form name="frm" action="" method="post" onSubmit="return validate();">

Play Football<input name="hobby1" type="checkbox" value="play_football" /><br>
Play Music<input name="hobby2" type="checkbox" value="play_music" /><br>
Listen Music<input name="hobby3" type="checkbox" value="listen_music" /><br>
Reading Newspaper<input name="hobby4" type="checkbox" value="reading_newspaper" />

<div id="msg" style="color:#FF0000"></div>
<input name="btn" type="submit" value="submit">
</form>
</body>
</html>

You can download source code here