hola es javascript
seria algo asi
<-- Codigo ofrecido por Tutores.org -->
<script>
function todos(chkbox)
{
for (var i=0;i < document.forms[0].elements.length;i++)
{
var elemento = document.forms[0].elements[i];
if (elemento.type == "checkbox")
{
elemento.checked = chkbox.checked
}
}
}
</script>
<form name="formulario" method="post" action="">
<table width="300" border="0" align="center" cellpadding="2" cellspacing="1">
<tr>
<td width="12" bgcolor="#eeeeeee"><font size="2" face="verdana">
<input type="checkbox" name="checkbox" value="checkbox">
Emails</font></td>
</tr>
<tr>
<td bgcolor="#999999"><font size="2" face="verdana">
<input type="checkbox" name="checkbox2" value="checkbox">
Asp</font></td>
</tr>
<tr>
<td bgcolor="#eeeeeee"><font size="2" face="verdana">
<input type="checkbox" name="checkbox3" value="checkbox">
Php</font></td>
</tr>
<tr>
<td bgcolor="#999999"><font size="2" face="verdana">
<input type="checkbox" name="checkbox4" value="checkbox">
Cgi</font></td>
</tr>
<tr>
<td bgcolor="#eeeeeee"><font size="2" face="verdana">
<input type="checkbox" name="checkbox5" value="checkbox">
Visualbasic</font></td>
</tr>
<tr>
<td bgcolor="#999999"><font size="2" face="verdana">
<input type="checkbox" name="checkbox6" value="checkbox">
Asp.net</font></td>
</tr>
<tr>
<td bgcolor="#eeeeeee"><font size="2" face="verdana">
<input type="checkbox" name="checkbox7" value="checkbox">
Applets</font></td>
</tr>
<tr>
<td bgcolor="#999999"><font size="2" face="verdana">
<input type="checkbox" name="checkbox8" value="checkbox">
Foros</font></td>
</tr>
<tr>
<td bgcolor="#eeeeeee"><font size="2" face="verdana">
<input type="checkbox" name="checkbox9" value="checkbox">
Tutores</font></td>
</tr>
<tr>
<td bgcolor="#999999"><font size="2" face="verdana">
<input type="checkbox" name="checkbox10" value="checkbox">
Tutoriales</font></td>
</tr>
<tr>
<td bgcolor="#990000"><input type="checkbox" name="checkbox11" value="checkbox" onClick="todos(this);">
<font color="#FFFFFF" size="2" face="Verdana"><strong> Seleccionar
todos Todos</strong></font></td>
</tr>
</table>
</form>