For IE 7 & 8 (and other browsers without CSS3 support not including IE6) you can try using the following to get the 2nd and 3rd children:
For 2nd Child, use this:
td:first-child + td
For 3rd Child, use this:
td:first-child + td + td
Now, simply you can add another + td for each additional child you wish to select.
But, If you want to support IE6 that can be done too! You just need to use a little javascript like this:
$(function() {
$('td:first-child').addClass("firstChild");
$(".table-class tr").each(function() {
$(this).find('td:eq(1)').addClass("secondChild");
$(this).find('td:eq(2)').addClass("thirdChild");
});
});
Then for your CSS you just need to use those class selectors to make whatever changes you like:
table td.firstChild { /*stuff here*/ }
table td.secondChild { /*stuff to apply to second td in each row*/ }