Email validation using 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;
 }
}
- Call the function on Email textbox
