Prova questo script ....

codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
<style type="text/css">
<!--
.normal1 {font-family:tahoma;font-size:8pt;background-color:yellow}
.normal2 {font-family:tahoma;font-size:8pt;background-color:white}
.overTR  {font-family:tahoma;font-size:8pt;background-color:blue;color:white}
.clicked {font-family:tahoma;font-size:8pt;background-color:red;color:white}
-->
</style>
<script language="JavaScript" type="text/javascript">
<!--
var aTR = null;
var aTbody = null;

function selectRow(aTD) {
 if (aTD.tagName == 'TD') {
  aTR     = aTD.parentElement;
	aTbody  = aTR.parentElement;
	document.getElementById('canc').disabled = false;
 } // if (aTD.tagName == 'TD')
} // function selectRow(aTD)

function _deleteRow(aTD) {
 if (aTR != null) {
	aTbody.deleteRow(aTR.rowIndex);
	aTR    = null;
	aTbody = null;
	document.getElementById('canc').disabled = true;
 } else {
  alert('Cliccare la riga da cancellare'); 
 } // if (aTR != null)
} // _deleteRow(aTD)
//-->
</script>


</head>
<body>
<table summary="" cellpadding="0" onclick="selectRow(event.srcElement)">
<tr  class="normal1" >
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
</tr>
<tr  class="normal2" >
<td>BBBBBBBBBBBBBBBBBBBBB</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
</tr>
<tr  class="normal1" >
<td>CCCCCCCCCCCCCCCCCCCCC</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
</tr>
<tr  class="normal2" >
<td>DDDDDDDDDDDDDDDDDDDDD</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
<td>AAAAAAAAAAAAAAAAAAAAA</td>
</tr>
</table>


<span style="font-family:tahoma;font-size:8pt">cliccare su una riga per attivare il bottone</style>

<input type="button" value="Canc" id="canc" disabled onclick="_deleteRow()">

</body>
</html>