Warning: mysql_connect()

estou com o seguinte arquivo de conexao.php

<?php
session_start();
ob_start();
$server = "mysql.hostinger.com.br";
$banco = "banco";
$usuario = "usuario";
$senha = "senha";

$conexao = mysql_connect($server, $usuario, $senha) or die (mysql_error());

$conexao = mysql_select_db("$banco", $conexao) or die (mysql_error());

mysql_query("SET NAMES 'utf8'");
mysql_query("SET caracter_set_connection=utf8");
mysql_query("SET caracter_set_client=utf8");
mysql_query("SET caracter_set_results=utf8");
?>

e esta aparecendo o seguinte erro em todas as paginas q tem include 'conexao.php'

Warning: mysql_connect() [function.mysql-connect]: Headers and client library minor version mismatch. Headers:50535 Library:100011 in/home/u232034955/public_html/odontomaster/conexao.php on line 6

Problemas no host ou no arquivo??????