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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Form - validate - Exg</title>
<script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
<form method="post" name="myForm">
<span class="formError email">Please Enter Valid Email</span>
<input type="text" name="Email" id="email" onKeyUp="checkEmail()" />
<input type="submit" value="Send" name="submitButton" />
</form>
<style>
.formError{ display:none; }
</style>
<script type="text/javascript">
function checkEmail(){
var email = $("#email").val();
var atpos=email.indexOf("@");
var dotpos=email.lastIndexOf(".");
if(email=='') $('.email').show();
else if (atpos<1 || dotpos<atpos+2 || dotpos+2>=email.length) $('.email').show();
else $('.email').hide()
}
</script>
</body>
</html>