$(document).ready(function() {

    // check the title field
    $('input[name=title]').keyup(function() {
        name = name.toLowerCase(); // lowercase
        name = name.replace(/^\s+|\s+$/g, ''); // remove leading and trailing whitespaces
        name = name.replace(/\s+/g, '-'); // convert (continuous) whitespaces to one -
        name = name.replace(/[^a-z-]/g, ''); // remove everything that is not [a-z] or -
        $('input[name=url]').val(name); // set value
    });
});