カレンダーにメモ機能をつけたい

カレンダーの日付のところにメモ機能をつけるためにテキストエリアをつけたいのですがどうしても入れることができません

JavaScript
1コード
2```<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
3<html>
4<head>
5  ・・・・・・・・・
6<link href="calender.css" rel="stylesheet" type="text/css">
7<script type="text/javascript"><!--
8var monthdays = new Array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
9var days = new Array("日", "月", "火", "水", "木", "金", "土");
10// 祝日1：何月の何日か？
11var Holidays1 = new Array(1,1, 2,11, 3,21, 4,29, 5,3, 5,4, 5,5, 9,23, 11,3, 11,23, 12,23);
12// 祝日2：何月の第何月曜日か？
13var Holidays2 = new Array(1,2, 7,3, 9,3, 10,2);
14// 現在の年、月、日の取得
15var now = new Date();
16var thisYear = now.getFullYear();
17var thisMonth = now.getMonth() + 1;
18var today = now.getDate();
19// 表示年月の記憶
20var year = thisYear;
21var month = thisMonth;
22function showCalen(n) {
23  month += n;
24  if (month == 0) { year--; month=12; }
25  else if (month == 13) { year++; month = 1; }
26  var flag = (year == thisYear && month == thisMonth) ? 1: 0;
27  var date = new Date(year, month-1, 1);  // 表示月の 1日の Date()
28  var startDay = date.getDay();
29  var dateMax = monthdays[month - 1];
30  if (month == 2 && ((year%4 == 0 && year%100 != 0) || year%400 == 0)) dateMax = 29;
31  // 休日配列の初期化
32  var holidays = new Array();
33  for (var i = 0; i <= dateMax; i++) holidays[i] = 0;
34  // 祝日1 の処理
35  var firstSunday = (startDay == 0) ? 1: 8 - startDay;
36  for (i = 0; i < Holidays1.length; i += 2) {
37    if (Holidays1[i] == month) {
38      holidays[Holidays1[i+1]] = 1;
39      for (var j = firstSunday; j < dateMax; j += 7)
40        if (Holidays1[i+1] == j ) { holidays[j+1] = 1; break; }  // 振替休日
41    }
42  }
43  // 祝日2 の処理
44  var mondays = new Array();
45  var firstMonday = (startDay < 2) ? 2 - startDay: 9 - startDay;
46  for (i = 0; i < Holidays2.length; i += 2)
47    if (Holidays2[i] == month) holidays[(Holidays2[i+1] - 1) * 7 + firstMonday] = 1;
48  var htmlStr = "<table class='calen'>\n" + "<tr class='bg1'><th colspan=7>"
49    + year + "年 " + month + "月</th></tr>\n";
50  htmlStr += "<tr class='bg2'><th class='sun'>" + days[0] + "</th>";
51  for (i = 1; i < 6; i++) htmlStr += "<th>" + days[i] + "</th>";
52  htmlStr += "<th class='sat'>" + days[6] + "</th></tr>\n";
53  var col = 0;
54  if (startDay > 0) {
55    htmlStr += "<tr>";
56    for ( ; col < startDay; col++) htmlStr += "<td>&nbsp;</td>";
57  }
58  for (i = 1; i <= dateMax; i++) {
59    if (col == 0) htmlStr += "<tr>";
60    if (flag == 1 && i == today) {
61      if (holidays[i] == 1 || col == 0) htmlStr += "<td class='today sun'>";
62      else if (col == 6) htmlStr += "<td class='today sat'>";
63      else htmlStr += "<td class='today'>";
64    }
65    else if (holidays[i] == 1 || col == 0) htmlStr += "<td class='sun'>";
66    else if (col == 6) htmlStr += "<td class='sat'>";
67    else htmlStr += "<td>";
68    htmlStr += i + "</td>";
69    if (col == 6) { htmlStr += "</tr>\n"; col=0; } else col++;
70  }
71  if (col != 0) {
72    for ( ; col < 7; col++) htmlStr += "<td>&nbsp;</td>";
73    htmlStr += "</tr>";
74  }
75  htmlStr += "</table>";
76  document.getElementById("calen").innerHTML = htmlStr;
77}
78//-->
79</script>
80</head>
81<body onload="showCalen(0)">
82<p><input type="button" value="前月" onclick="showCalen(-1)">
83<input type="button" value="次月" onclick="showCalen
84<div id="calen"></div>
85</body>
86</html>