The following checks if anything at all has been entered.

Code:
$('#contact-form #submit').click(function () {

                //Get the data from all the fields
                var name = $('input[name=name]');
                var email = $('input[name=email]');
                var website = $('input[name=url]');
                var message = $('textarea[name=message]');

                //Simple validation to make sure user entered something
                //If error found, add hightlight class to the text field
                if (name.val()=='') {
                    name.addClass('hightlight');
                    return false;
                } else name.removeClass('hightlight');

                if (email.val()=='') {
                    email.addClass('hightlight');
                    return false;
                } else email.removeClass('hightlight');

                if (message.val()=='') {
                    message.addClass('hightlight');
                    return false;
                } else message.removeClass('hightlight');

            });
How can I use a regular expression to check for a valid email?

Sorry, I'm really new at this.