表格隔行变色和鼠标滑过变色

****不会影响到tr中的th****

jquery代码

<script>
$(document).ready(function(){
    $("#mytable tr:even td").css("background","#ccc");
    $("#mytable tr:even td").attr("bg","#ccc");
    $("#mytable tr:odd td").attr("bg","#fff");
    $("#mytable tr td").hover(function(){
        $(this).parent().find("td").css("background","#000")
        },function(){
            var bgc = $(this).attr("bg");
            $(this).parent().find("td").css("background",bgc)
            });
       })
</script>

HTML代码

<table width="100%" border="0" cellspacing="0" cellpadding="0" id="mytable">
<tr>
    <th>1</th>
    <th>2</th>
    <th>4</th>
    <th>&nbsp;</th>
  </tr>
  <tr>
    <td>1</td>
    <td>2</td>
    <td>4</td>
    <td>&nbsp;</td>
  </tr>
  <tr>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
  </tr>
</table>