function showMenu(tab)
{ 
 i=1;
    while (document.getElementById("m_"+i))
 {
 document.getElementById("m_"+i).style.visibility='hidden'; 
 i++;
 }
 document.getElementById(tab).style.visibility='visible';
}
function subshowMenu(st)
{ 
 i=1;
    while (document.getElementById("s_"+i))
 {
 document.getElementById("s_"+i).style.visibility='hidden'; 
 i++;
 }
 document.getElementById(st).style.visibility='visible';
}


function hideMenu(tab)
{  
 document.getElementById(tab).style.visibility='hidden'; 
 }