function validate_form (obj_form) {
	obj_form.first_name.value = trim ( obj_form.first_name.value );
	obj_form.last_name.value = trim ( obj_form.last_name.value );
	obj_form.email.value = trim ( obj_form.email.value );

	if ( obj_form.first_name.value == "" ) {	
		obj_form.first_name.focus ();
		alert ( "Le prénom est un champ obligatoire." );
		return false;
	}
	if ( obj_form.last_name.value == "" ) {	
		obj_form.last_name.focus ();
		alert ( "Le nom est un champ obligatoire." );
		return false;
	}
	if ( obj_form.email.value == "" ) {	
		obj_form.email.focus ();
		alert ( "L’adresse électronique est un champ obligatoire." );
		return false;
	} else if ( !isEmail(obj_form.email.value)) {	
		obj_form.email.focus ();
		alert ( "Vous devez entrer une adresse électronique valide." );
		return false;
	}
	
	return true;
}