function show_menu(menu_content,pos) {
  var menu;
  if (document.all) {menu=document.all.menu;}
  else {menu = document.getElementById("menu");}
  menu.innerHTML = "<span class='left-menu' style='margin-left:"+pos+"px'><span class='right-menu'><span class='middle-menu'>" + menu_content + "</span></span></span>";
}
function show_about_cbt() {
  show_menu("<a href='about.html'>Our School</a> | <a href='whoisdavid.html'>Who's David</a>",0);
}
function show_toeic() {
  show_menu("<a href='toeic.html'>TOEIC Course</a> | <a href='toeic_about.html'>About TOEIC</a> | <a href='toeic_schedule.html'>More Information</a>",20);
}
function show_toefl() {
  show_menu("<a href='toefl.html'>TOEFL Course</a> | <a href='toefl_about.html'>About TOEFL</a> | <a href='toefl_schedule.html'>More Information</a>",40);
}