You should NEVER rely on client-side validation of data entered in a web-based form. Since the validation takes place on the client’s side, it is really out of your control, and thus is not reliable (they could bypass/modify the requirements without your knowledge). On top of that – this library only works with Internet Explorer, so users with a different browser will not have their information validated at all!
This library is in use on a number of commercial sites, including on the contact form of this website!
- Tag-level understanding of HTML is important