Javascript select yardım ???

<script type="text/javascript">
function dropdown(combo_0) {
   if(combo_0.options.selectedIndex > 1){ 
      return false; 
   } else { 
   if(c){ combo_0.form.submit(); } 
   } 
}

function showMe(blockId) {
     if ( document.getElementById(blockId).style.display == 'none' ) {
          document.getElementById(blockId).style.display = ''; }
else if ( document.getElementById(blockId).style.display == '' ) {
          document.getElementById(blockId).style.display = 'none'; }
}
</script>
<table width="100%" border="0">
                  <tr>
                   <td><strong>Ülkeler:</strong></td>
                   <td><select name="combo_0" id="combo_0" onchange="dropdown(this),showMe('mesaj','buton')" style="width:200px;">
                      <option value="0">---- Lütfen Seçiniz ----</option>
                      <option value="1">TÜRKİYE</option>
                      <option value="2">ALMANYA</option>
                      <option value="3">AMERİKA</option>
                      <option value="4">ANGOLA</option>
                      <option value="5">ARJANTİN</option>
                      <option value="6">ARUHA</option>
                      <option value="7">AVUSTRALYA</option>
						</select></td>
                   </tr>
                  <tr>
                    <td colspan="2"><div id="mesaj" style="display:none;"><layer><big>Bu ülkeyi seçemezsin!!!</big></layer></div></td>
                  </tr>
</table>