Error Fatal

[Veronicalismar]

Fatal error: Call to undefined function mysql_connect() in

Que quiere decir este error??

esta es la funcion que tengo

function connect()
{
// connect to mysql
$this->link = mysql_connect($this->db_host, $this->db_user, $this->db_pwd)
or die("Could not connect to mysql server: " . mysql_error());
// connect to the database
mysql_select_db($this->db_name, $this->link)
or die("Database: database not found");
$this->connections++;
// return $db_link for other functions
//return $link;
}