function check_input(field_name, field_size) {
    var field_value = document.getElementById(field_name).value;
	
    if (field_value == '' || field_value.length < field_size) {
		error = true;
    }
}

function check_form_recherche(){
  	error = false;
	form = document.form_recherche;

	check_input("titre", 2);
	check_input("description", 2);
	check_input("mots_cles", 2);
	
	if (error == true) {
		document.getElementById('warning').style.display="block";
		return false;
	} else {
		return true;
	}
}