Пример с использованием CSS и JS


<html>
<head>
<style>
td
{
border: 1px solid gray;
}
</style>
<script language="javascript">
function onm(th)
{
th.style.border="1px solid red";
}

function outm(th)
{
th.style.border="1px solid gray";
}
</script>
</head>
<body>
<table border="1">
  <tr>
    <td onmouseover="onm(this)" onmouseout="outm(this)">Text 1</td>
    <td onmouseover="onm(this)" onmouseout="outm(this)">Text 2</td>
  </tr>
  <tr>
    <td onmouseover="onm(this)" onmouseout="outm(this)">Text 3</td>
    <td onmouseover="onm(this)" onmouseout="outm(this)">Text 4</td>
  </tr>
  <tr>
    <td onmouseover="onm(this)" onmouseout="outm(this)">Text 5</td>
    <td onmouseover="onm(this)" onmouseout="outm(this)">Text 6</td>
  </tr>
</table>
</body>
</html>
Text 1 Text 2
Text 3 Text 4
Text 5 Text 6

Пример с использованием CSS (не работает в IE)


<html>
<head>
<style>
td
{
border: 1px solid gray;
}
td:hover
{
border: 1px solid red;
}
</style>
</head>
<body>
<table border="1">
  <tr>
    <td>Text 1</td>
    <td>Text 2</td>
  </tr>
  <tr>
    <td>Text 3</td>
    <td>Text 4</td>
  </tr>
  <tr>
    <td>Text 5</td>
    <td>Text 6</td>
  </tr>
</table>
</body>
</html>
Text 1 Text 2
Text 3 Text 4
Text 5 Text 6