Problem z funkcją JavaScript w firefox

Kod:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">

<HTML xmlns="http://www.w3.org/1999/xhtml" lang="pl" xml:lang="pl">

<HEAD>

tutaj oczywiście wszelkie mety oraz title

<SCRIPT LANGUAGE="JavaScript">

    var zkontakt; var zgaleria; var zoferta; var zcennik;

     function clicked (button)

     {

     if (button=="kontakt")

        {

        zkontakt="true";

        zgaleria="false"

        zoferta="false"

        zcennik="false"

        galeria.src="buttony/galeria_off.jpg"

        oferta.src="buttony/oferta_off.jpg"

        cennik.src="buttony/cennik_off.jpg"

      }

      else if (button=="galeria")

      {

        zkontakt="false";

        zgaleria="true"

        zoferta="false"

        zcennik="false"

    kontakt.src="buttony/kontakt_off.jpg"

    oferta.src="buttony/oferta_off.jpg"

    cennik.src="buttony/cennik_off.jpg"

        galeria.src="buttony/galeria_on.jpg"

      }

      else if (button=="oferta")

      {

        zkontakt="false";

        zgaleria="false"

        zoferta="true"

        zcennik="false"

    kontakt.src="buttony/kontakt_off.jpg"

        galeria.src="buttony/galeria_off.jpg"

        cennik.src="buttony/cennik_off.jpg"

      }

      else if (button=="cennik")

      {

        zkontakt="false";

        zgaleria="false"

        zoferta="false"

        zcennik="true"

    kontakt.src="buttony/kontakt_off.jpg"

        galeria.src="buttony/galeria_off.jpg"

        oferta.src="buttony/oferta_off.jpg"

      }

     }



     function odznacz()

     {

     if (zkontakt!="true")

      {

        kontakt.src="buttony/kontakt_off.jpg"

      }

     if (zgaleria!="true")

      {

        galeria.src="buttony/galeria_off.jpg"

      }

      if (zoferta!="true")

      {

        oferta.src="buttony/oferta_off.jpg"

      }

      if (zcennik!="true")

      {

        cennik.src="buttony/cennik_off.jpg"

      }

      //mkontakt.src="buttony/kontakt_off.jpg"

     }





      </script>

</head>

<body>



<table style="border: solid black 0px" BORDER="0" CELLSPACING="0" CELLPADDING="0">

<tr>

<td>

<a target="ramka" onMouseOver='galeria.src="buttony/galeria_on.jpg"'

onMouseOut='odznacz()' onClick='clicked("galeria")'>

<img src="buttony/galeria_off.jpg" name="galeria" border="0"></a>



</td><td>

<a target="ramka" href="kontakt.htm" onMouseOver='kontakt.src="buttony/kontakt_on.jpg"'

onMouseOut='odznacz()' onClick='clicked("kontakt")'>

<img src="buttony/kontakt_off.jpg" name="kontakt" border="0"></a>



</td><td>

<a target="ramka" href="oferta.htm" onMouseOver='oferta.src="buttony/oferta_on.jpg"'

onMouseOut='odznacz()' onClick='clicked("oferta")'>

<img src="buttony/oferta_off.jpg" name="oferta" border="0"></a>



</td><td>

<a target="ramka" href="cennik.htm" onMouseOver='cennik.src="buttony/cennik_on.jpg"'

onMouseOut='odznacz()' onClick='clicked("cennik")'>

<img src="buttony/cennik_off.jpg" name="cennik" border="0"></a> 

</td>

</tr>

</body>

</html>