Edit in JSFiddle

$("#btnSubmit").click(function () {
    //validate email
    var email = $("#txtEmailID").val();
    if(!validateEmail(email))
    {
        alert('Invalid Email ID');
        $("#txtEmailID").focus();
        return;
    }
    
    alert('Form submitted');
});

function validateEmail(email) {
    var filter = /^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/;
    if (filter.test(email)) {
        return true;
    } else {
        return false;
    }
}

<input id="txtEmailID" type="text" />
<br /><br />
<input id="btnSubmit" type="submit" value="submit" />