if(document.getElementById){document.onkeydown=navigate;}

function navigate(key){
  var code;
  if(!key){var key=window.event;}
  if(key.keyCode){
    code=key.keyCode;
  }else{
    if(key.which){code=key.which;}
  }
  if((code==37)&&(key.ctrlKey==true)){
    var destination=document.getElementById('pb');
    if(destination){document.location.href=destination.href;}
  }
  if((code==39)&&(key.ctrlKey==true)){
    var destination=document.getElementById('pf');
    if(destination){document.location.href=destination.href;}
  }
}