<form action="login.php" method="post" name="FormLogin" onsubmit="return validalogin();">
 <div class="mainContentTitolo1">Inserisci i dati</div>
      <div class="table">
        <div class="tr">
            <div class="th">
               <label for="username">Nome Utente.</label>
            </div>
            <div class="td">
               <input type="text" name="username" id="username" accesskey="m" tabindex="1" size="20" maxlength="16" value=""/>
            </div>
        </div>
        <div class="tr">
            <div class="th">
                <label for="password">Password</label>
            </div>
            <div class="td">
               <input type="password" name="password" id="password" accesskey="p" tabindex="2" size="20" maxlength="16" value=""/>
       </div>
     </div>
         <input type="hidden" name="refer" value="$refer" />
         <input type="hidden" name="invio" value="1" />
         <div class="tr">
             <div class="tdcolspanallcenter">
                  <input type="image" src="../../images/conferma.gif" tabindex="3" alt="Conferma login" onclick="return validalogin();" />
             </div>
          </div>
          <div class="tr">
                <div class="tdcolspanallcenter">Collegati
                </div>
          </div>
      </div>
</form>

https://.../login.php?username=BROWN&password=FOX

[...]
<input type="text" name="username" id="username" accesskey="m" tabindex="1" size="20" maxlength="16" value="BROWN"/>
[...]
<input type="password" name="password" id="password" accesskey="p" tabindex="2" size="20" maxlength="16" value=""/>
[...]