remove the http:// from user_contactmethods

hi . i add some filed to user form with this code :

function modify_contact_methods($profile_fields) {
	$profile_fields['digreepost'] = 'درجه';
	$profile_fields['cityofuser'] = 'شهر / استان';
	$profile_fields['idyahoomessenger'] = 'آیدی یاهو';
	$profile_fields['expdateshowpost'] = 'تاریخ انقضا';
	return $profile_fields;
}
add_filter('user_contactmethods', 'modify_contact_methods');

but this save the value with http://
i could remove that with str_replace but i want use without it.