function switch_content( id )
{

 var obj=document.getElementById(id);//.className='show_content';
 if( obj.className=='show_content' )
  {
  	obj.className='hidden_content';
  }else
  {
 	obj.className='show_content';
  }
}

function change_img( obj, img_src )
{
 obj.src=img_src;
}