Here's a quick way of doing it, though not strictly validated (v4.1.x) ...
skin1/main/register_contact_info.tpl
after...
Code:
{if $default_fields.email.avail eq 'Y'}
add...
Code:
{literal}
<script type="text/javascript" language="javascript">
function check_email(){
var theForm = document.forms['registerform'];
var errMsg = "";
var setfocus = "";
if (theForm['email2'].value != theForm['email'].value){
errMsg = "E-Mail confirmation does not match!";
setfocus = "['email2']";
}
if (errMsg != ""){
alert(errMsg);
eval("theForm" + setfocus + ".focus()");
}
}
</script>
{/literal}
Then after,
Code:
<tr>
<td align="right">{$lng.lbl_email}</td>
<td>{if $default_fields.email.required eq 'Y'}<font class="Star">*</font>{else} {/if}</td>
<td nowrap="nowrap">
<input type="text" id="email" name="email" size="32" maxlength="128" value="{$userinfo.email}" />
{if $emailerror ne "" or ($reg_error ne "" and $userinfo.email eq "" and $default_fields.email.required eq 'Y')}<font class="Star"><<</font>{/if}
</td>
</tr>
and before {/if}
add...
Code:
<tr>
<td align="right">Confirm {$lng.lbl_email}</td>
<td><font class="Star">*</font></td>
<td nowrap="nowrap">
<input type="text" id="email2" name="email2" size="32" maxlength="128" value="" onBlur="check_email();" />
</td>
</tr>