Ok amigo te entiendo pero me da dos errores, te los muestro:
Código PHP:
<?php
$id = $_GET['id'];
$idg = $_POST['idg'];
//$idg = $_GET['idg'];
//$idg = isset($_GET["idg"])? $_GET["idg"]: '';
require ("funciones2.php");
$idc = conectar();
$sql = "SELECT * FROM musica WHERE idg=$idg";
//$sql="SELECT * FROM musica m, generos g WHERE m.idg = g.idg";
$res = ejecutar($sql,$idc);
$fila = getRegistro ($res);
$sql = "DELETE FROM musica WHERE idg=$idg";
//$sql = "DELETE generos FROM generos g, musica m WHERE g.idg = m.idg";
$res = ejecutar($sql,$idc);
$sql = "SELECT * FROM musica WHERE id=$id";
$res = ejecutar($sql,$idc);
$fila = getRegistro ($res);
$sql = "DELETE FROM musica WHERE id=$id";
$res = ejecutar($sql,$idc);
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Sistema de rock</title>
<link href="formato1.css" rel="stylesheet" type="text/css" />
</head>
<body>
<?php
if ($res)
echo "ELIMINACIÓN EXITOSA";
else
echo "ERROR";
?>
<br/>
<br/>
</body>
</html>
<?php
cerrar ($idc);
?>
Notice: Undefined index: idg in C:\wamp\www\Edward-Relaciones\eliminar.php on line 4
Call Stack
# Time Memory Function Location
1 0.0032 143944 {main}( ) ..\eliminar.php:0
( ! ) Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in C:\wamp\www\Edward-Relaciones\funciones2.php on line 22
Call Stack
# Time Memory Function Location
1 0.0032 143944 {main}( ) ..\eliminar.php:0
2 0.0053 155752 getRegistro( ) ..\eliminar.php:18
3 0.0053 155800 mysql_fetch_array ( ) ..\funciones2.php:22
ELIMINACIÓN EXITOSA
Y no borra el registro de la tabla generos.