A while ago I put up a Password Strength Checker using JavaScript and Regular Expressions. On that same note, you can also check the structure of an email address utilizing the same methodology: If your form element has the id=emailaddress and you add a form onSubmit=”return checkEmail();”, this is a Javascript function that you can utilize to return an alert if the email address has a valid structure or not: <script language="javascript"> function checkEmail() { var email = document.getElementById(‘emailaddress’); 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 … Continue reading →