// JavaScript Document
<!-- News letter subscription validation -- STARTS-->
function subscribe(){

	if(document.getElementById("news").value == 0)
	{
		alert("Please enter E-Mail address.")
		document.getElementById("news").focus()
		return false
	}
	else if(document.getElementById("news").value!=0)
	{
		if(!isValidEmail())
		{
			alert("Please enter valid Email Id")
			document.getElementById("news").focus()
			return false
		}
		else
		{
			return true
		}
	}
	else
		return true
}

function isValidEmail()
{ 
	var emailID=document.getElementById('news');	
	var RegExp = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*\.(\w{2}|(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum))$/
	if(!RegExp.test(emailID.value))
	{ 
		return false;
	} 
	else
	{
		return true;
	}
}
<!-- News letter subscription validation -- ENDS-->