Problems Changing Signup.html

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OBJECTIVE:
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Change signup.html to use ONLY the following fields for signup:

First Name
Email Address
Password

NO OTHER FIELDS

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SIGNUP.HTML AFTER CHANGE:
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{assign var="title" value="Sign-up"} {include file="header.html"}
<center>
<br>
<div class=hdr>{$title}</div>
<hr>
<a name="e">&nbsp;</a> {if $error}
<table>
<tr>
<td> {foreach from=$error item=e}
<li><font color=red><b>{$e}</b></font> {/foreach}
</td>
</tr>
</table>
{/if}
<form name=signup method=post action="signup.php#e">
<input type=hidden name=product_id value=1>
<table align=center class=vedit>
<tr>
<th width=40%><b>Your First Name</b><br>
</th>
<td nowrap>
<input type=text name=name_f value="{$smarty.request.name_f|escape}" size=15>
</td>
</tr>
<tr>
<th width=40%><b>Your E-Mail Address</b><br>
<small>A confirmation email will be sent<br>
to you at this address</small></th>
<td nowrap>
<input type=email name=email value="{$smarty.request.email|escape}" size=30>
</td>
</tr>
{if not $config.generate_login}
<script>

function checkUniqLogin(){
var login=document.forms['signup'].elements['login'].value;
var email=document.forms['signup'].elements['email'].value;
{/literal}{if not $config.generate_pass}
var word=document.forms['signup'].elements['pass0'].value;
{else}
var word="";
{/if}{literal}
window.open('uniq_login.php?login='+login+'&email='+email+'&word='+word, '',
'dependent=1,directories=0,height=400,width=300,location=0');
}
</script>
{/if} {if not $config.generate_pass}
<tr>
<th><b>Choose a Password</b><br>
<small>Must be {$config.pass_min_length} or more characters</small></th>
<td nowrap>
<input type=password name=pass0 value="{$smarty.request.pass0|escape}" size=15 maxlength=15>
</td>
</tr>
<tr>
<th><b>Confirm your password</b><br>
<small>Enter password again</small></th>
<td nowrap>
<input type=password name=pass1 value="{$smarty.request.pass1|escape}" size=15 maxlength=15>
</td>
</tr>
{/if} {$additional_fields_html}
</table>
<br>
<input type=hidden name=do_payment value=1>
<input type=hidden name=price_group value="{$smarty.request.price_group|escape}">
<input type=submit value="Continue">
</form>
</center>
{include file="footer.html"}

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ERRORS DISPLAYED WHEN SUBMIT FORM
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Please enter your Last Name
Please enter valid Login Name. It must contain at least 4 characters

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QUESTIONS/STATEMENTS
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I don't want to delete the error code processing at the top of the page because I don't think this is the right approach.

Since I do not use Last Name, First Name only, I need to eleminate this error. How?

Since I am using First Name only a 4 char name such as Don is valid. How do I eleminate this error properly?

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BOTTOM LINE QUESTION
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Can I use aMember with a signup page that uses only first name, email and password, and still have the aMember system work?

Thanks.