实现一次全选

<script language="javascript">

function CheckAll(){
 var obj = document.del('delid[]');
 var length = obj.length;
 if (length > 1) {
  for (i=0; i<length; i++) {
   var obj1 = obj[i];
   obj1.checked = !obj1.checked;
  }
 }
 else if (length == 0) {
  return;
 }
 else {
  obj.checked = !obj.checked;
 }
}

</script>

<FORM name=del id="del" action=test.php method=post>
      <TABLE cellSpacing=1 cellPadding=3 width="100%" bgColor=#e7e3e7>
        <TBODY>
        <TR align=middle>
          <TD class=head width="6%">ID</A></TD>
          <TD class=head width="40%">标题</TD>
          <TD class=head width="10%">发件人</TD>
          <TD class=head width="10%">收件人</TD>
          <TD class=head width="20%">时间</TD>
          <TD class=head width="7%">已读</TD>
          <TD class=head width="7%">选定</A></TD></TR><!---->
        <TR class=f_one align=middle>
          <TD>1</TD>
          <TD align=middle><A
            href="http://www.niuguo.net/message.php?action=read&amp;mid=366560">寻秦记</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=14425">898989</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=54639">wwd</A></TD>
          <TD class=smalltxt span>2006-01-10 11:08</TD>
          <TD align=middle><!---->是 <!----></TD>
          <TD align=middle><!----><INPUT type=checkbox value=366560
            name=delid[]> <!----></TD></TR><!---->
        <TR class=f_one align=middle>
          <TD>2</TD>
          <TD align=middle><A
            href="http://www.niuguo.net/message.php?action=read&amp;mid=366534">~~~~~~~~~~~</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=10903">cjccjc</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=54639">wwd</A></TD>
          <TD class=smalltxt span>2006-01-10 08:29</TD>
          <TD align=middle><!---->是 <!----></TD>
          <TD align=middle><!----><INPUT type=checkbox value=366534
            name=delid[]> <!----></TD></TR><!---->
        <TR class=f_one align=middle>
          <TD>3</TD>
          <TD align=middle><A
            href="http://www.niuguo.net/message.php?action=read&amp;mid=366251">Re:你好！兄弟，从29集以后传吧，..</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=14425">898989</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=54639">wwd</A></TD>
          <TD class=smalltxt span>2006-01-08 00:31</TD>
          <TD align=middle><!---->是 <!----></TD>
          <TD align=middle><!----><INPUT type=checkbox value=366251
            name=delid[]> <!----></TD></TR><!---->
        <TR class=f_one align=middle>
          <TD>4</TD>
          <TD align=middle><A
            href="http://www.niuguo.net/message.php?action=read&amp;mid=365840">~~~~^^</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=10903">cjccjc</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=54639">wwd</A></TD>
          <TD class=smalltxt span>2006-01-05 20:50</TD>
          <TD align=middle><!---->是 <!----></TD>
          <TD align=middle><!----><INPUT type=checkbox value=365840
            name=delid[]> <!----></TD></TR><!---->
        <TR class=f_one align=middle>
          <TD>5</TD>
          <TD align=middle><A
            href="http://www.niuguo.net/message.php?action=read&amp;mid=365692">Re:你好！</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=14425">898989</A></TD>
          <TD align=middle><A
            href="http://www.niuguo.net/profile.php?action=show&amp;uid=54639">wwd</A></TD>
          <TD class=smalltxt span>2006-01-04 17:56</TD>
          <TD align=middle><!---->是 <!----></TD>
          <TD align=middle><!----><INPUT type=checkbox value=365692
            name=delid[]> <!----></TD></TR><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----></TBODY></TABLE>
      <BR>
      <CENTER><INPUT οnclick=CheckAll(del) type=button value=全选 name=chkall>
<INPUT type=submit value=提交>
<INPUT
      type=radio CHECKED value=del name=action>删除
  </CENTER></FORM>