请问JS中怎样设置一个表格的某行隐藏不显示

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<SCRIPT LANGUAGE="JavaScript">
<!--//-->
</SCRIPT>
</HEAD><BODY>
<TABLE>
<TR id=op>
<TD>1</TD>
<TD>1</TD>
<TD>1</TD>
</TR>
<TR>
<TD>2</TD>
<TD>2</TD>
<TD>2</TD>
</TR>
</TABLE>
<input type=button value="隐藏" onclick="document.all.op.style.display='none'">
<input type=button value="显示" onclick="document.all.op.style.display='block'"></BODY>
</HTML>