function check_username(login, email, update){
	if(!update)return;
		var signup_username = $('#'+login).val();
		if(!signup_username)return;
		if(email){
			var signup_email = $("#"+email).val();
		}
		//new Ajax.Request("/ajax/on_the_fly.php?signup_username="+signup_username+"&signup_email="+signup_email, opt);
		$.get("/ajax/on_the_fly.php?signup_username="+signup_username+"&signup_email="+signup_email,'',function(data){$("#"+update).html(data);$("#"+update).css("display","");});
}