show hide layer on tab clicking

function showDiv(dvnm)
{
 document.getElementById(dvnm).style.display = 'block';
 document.getElementById(dvnm).style.visibility = 'visible';
}

function hideDiv(dvnm)
{
 document.getElementById(dvnm).style.display = 'none';
 document.getElementById(dvnm).style.visibility = 'hidden';
}
function showlayer(n)
{
 for(i=1;i<=2;i++)//number of layer u want to show
 {
  if(i==n)
  {
   showDiv('div'+ i);//dynamically call div id
   document.getElementById('tab'+i).style.backgroundColor="#666666";//dynamically show contant id
  }
  else
  {
   hideDiv('div'+ i); 
      document.getElementById('tab'+i).style.backgroundColor="gray";
  }
 }
}