Per la prima domanda prova questo.

Codice PHP:
<!DOCTYPE html>
<html>
    <head>
   </head>
    <body>
        <script>
            function pippo(tagName,position,textToAdd) {
                position--;
                coll = document.getElementsByTagName(tagName);
                for(i=0;i<coll.length;i++) {
                    if (i==position) {
                        elem = coll[i];
                        elem.innerHTML += textToAdd;
                    }
                }
            }
        </script>
<table width=100% cellpadding=2 cellspacing=0 border=0>
<tr>
<td colspan=2 align="RIGHT"><font face="Arial"   size=2> I campi in <b>GRASSETTO</b> sono indispensabili   *</font></td>
</tr>
 <tr>
<td colspan=2 bgcolor=#3B5998>    <font face="Arial" size=2><font   color=#FFFFFF><b>Dati del   cliente</b></font></font>
</td>
</tr>       
<tr>
<td width=30% valign=middle align=right><font face="Arial" size=2><label for="bill_name">    <b class="required">* Nome e Cognome</b></label></font>
</td>     
<td width=70% valign=top><input id="bill_name" type=text   name="pd[0]" size=35 maxlength=50 value="">
</td>
</tr>
<tr>
<td width=30% valign=middle align=right><font face="Arial" size=2><label for="bill_company">    Azienda</label></font>
</td>     
<td width=70% valign=top><input id="bill_company"   type=text name="pd[15]" size=35 maxlength=40   value="">
</td>
</tr>     
</table>
<script>pippo("b",3," o ditta");
</Script>    
</body>
</html>