Show message instead of alert

Show message instead of alert

I am using this amazing javascript to check if all my fields are filled in
but instead of a alert box I want to show a message on my page instead
$(document).ready(function() {
$('form').submit(function() {
var incomplete = $('form :input').filter(function() {
return $(this).val() == '';
});
//if incomplete contains any elements, the form has not been filled
if(incomplete.length) {
alert('Vul alle velden in en probeer het nog eens');
//to prevent submission of the form
return false;
}
});
});
I tried to play with echo messages but that didn't worked