<script type="text/javascript">
//这个就是键盘触发的函数
var HandleKeyboard  = function(evt) {
  evt = window.event || evt;
  if(evt.keyCode == 13){ //如果取到的键值是回车
      //do something        
   } else {
      //其他键  dosomething
   }
}
window.document.onkeyup = HandleKeyboard;
</script>

附常用功能键
常数         值  描述
vbKeyBack     8  BACKSPACE 键
vbKeyTab      9  TAB 键
vbKeyReturn   13 ENTER 键
vbKeyShift    16 SHIFT 键
vbKeyControl  17 CTRL 键
vbKeyCapital  20 CAPS LOCK 键
vbKeyEscape   27 ESC 键
vbKeySpace    32 SPACEBAR 键
vbKeyPageUp   33 PAGEUP 键
vbKeyPageDown 34 PAGEDOWN 键
vbKeyEnd      35 END 键
vbKeyPrint    42 PRINT SCREEN 键
vbKeyDelete   46 DEL 键
vbKeyNumlock  144 NUM LOCK 键