jQuery Form Validation
Using the jQuery Validation plugin, you can simply add validation on clientside before submit form. The plugin also offering plenty of customization options. For a full overview of this plugin, check out the documentation.
Validation - Regular Style
Validating your form, just add the class .form-validate to any <form>, then it validate the form show error message.
Validation - Alternet Style
You can add .is-alter with .form-validate class then all the error message show different style.