in short: it's not really possible to know, because web pages are stateless. you cannot really know when a user stops looking at the page, closes the browser, turns off the pc etc ...you might check this
MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.
Things That Drive Us Nuts
Have you noticed the use of the reCaptcha feature at EE and other web sites? It wants you to read and retype something that looks like this.Insanity! It's not EE's fault - that's just the way reCaptcha works. But it is …
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions.
Consider email address RFCs:
Look at HTML5 form input element (with type=email) regex pattern: