使用CSS如何悬停背景颜色变色 onmouseover、onmouseout

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
<style type="text/css">
table {
	border-collapse:collapse;
}
td {
	border:#000 solid 1px;
}
</style>
</head>

<body>
<table width="600" border="1" cellspacing="0" cellpadding="0">
  <tr>
    <td onmouseover="this.style.background='#666666'" onmouseout="this.style.background=''"> </td>
    <td onmouseover="this.style.background='#666666'" onmouseout="this.style.background=''"> </td>
  </tr>
  <tr>
    <td onmouseover="this.style.background='#666666'" onmouseout="this.style.background=''"> </td>
    <td onmouseover="this.style.background='#666666'" onmouseout="this.style.background=''"> </td>
  </tr>
</table>
</body>
</html>