function check_username(){
	var username = getid('username').value;
	if (username.length<6 || username.length>12){
		showmsg('usr_name_msg','请输入6---12位任意字符');
		getid('usr_name_msg').className='b';
	}else{
		showmsg('usr_name_msg','昵称格式正确');
		getid('usr_name_msg').className='c';
	}
}