Email validation using JavaScript

<script language="javascript">

function checkEmail() {

    var email = document.getElementById('txtEmail');

    var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

    if (!filter.test(email.value)) {

    alert('Please provide a valid email address');

    email.focus;

    return false;

 }

}</script>

Take a textbox and button in your aspx page and call the JavaScript function on button click.

<input type='text' id='txtEmail'/>

<input type='submit' name='submit' onclick='Javascript:checkEmail();'/>