MySQL Cannot add foreign key constraint Error Code: 1215 - mysql

Question

I am making a simple MySQL database but i keep getting an error:Cannot add foreign key constraint any help appreciated!
Also a Side question is there any difference between using symbol ` and ' while creating your database?
/*!40101 SET NAMES utf8 */;
/*!40101 SET SQL_MODE=''*/;
/*!40014 SET #OLD_UNIQUE_CHECKS=##UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET #OLD_FOREIGN_KEY_CHECKS=##FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET #OLD_SQL_MODE=##SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET #OLD_SQL_NOTES=##SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`a3823833_MiniPost` /*!40100 DEFAULT CHARACTER SET latin1 */;
USE `a3823833_MiniPost`;
/*Table structure for table `user` */
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`userid` bigint(10) NOT NULL,
`username` varchar(20) NOT NULL,
`password` varchar(20) NOT NULL,
`email` varchar(50) NOT NULL,
PRIMARY KEY (`userid`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
/*Table structure for table `profile` */
DROP TABLE IF EXISTS `profile`;
CREATE TABLE `profile` (
`userid` int(11),
`lastName` varchar(50),
`firstName` varchar(50),
`dob` varchar(10),
PRIMARY KEY (`userid`),
CONSTRAINT `profile_fk` FOREIGN KEY (`userid`) REFERENCES `user` (`userid`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Answer 1

the bigint(10) and int(11) are not the same. make em same, and pk on parent table (as u are)