Java erreur

Bonjour,
quand jessai de compiler ce code:///////////////////////////////////////////////////////

package packagePricer;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;

public class GereConnexionSI
{
static final String DRIVER = "org.firebirdsql.jdbc.FBDriver";
static final String URL = "jdbc:firebirdsql:localhost/3050:";
static final String USER = "SYSDBA";
static final String PASSWORD = "masterkey";
private static Driver d = null;

public static Connection getConnexionSI(String nombase) throws Exception
{
d = (java.sql.Driver) Class.forName(DRIVER).newInstance();
java.sql.DriverManager.registerDriver(d);
return DriverManager.getConnection(URL + nombase, USER, PASSWORD);
}

///////////////////////////////////
je reçoi ce message d'erreur:///////////
java.lang.ClassNotFoundException: org.firebirdsql.jdbc.FBDriver
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at packagePricer.GereConnexionSI.getConnexionSI(GereConnexionSI.java:17)
at packagePricer.Testvar.<init>(Testvar.java:20)
at packagePricer.MainFormHandler.<init>(MainFormHandler.java:20)
at packagePricer.Main.main(Main.java:9)
///////////////////////////

Merci ++!!