function register(evt)
 {
  if (!evt)
   evt = window.event;

  if (evt.ctrlKey && !disKeyTrap)
   {
    switch(evt.keyCode)
     {
      case 37:
       aelt = document.getElementById('previous_page');
       if (aelt) location.href = aelt.href;
       break;

      case 39:
       aelt = document.getElementById('next_page');
       if (aelt) location.href = aelt.href;
       break;
     }
   }
 }

disKeyTrap = false;
document.onkeydown = register;