codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Pagina senza titolo</title>

<script language="javascript" type="text/javascript">
// <!CDATA[

function Button1_onclick() 
{
    var a = elementi_lista();
    for(var i = 0; i < a.length; i++)
    {
            alert(a[i].value);
    }
}

function elementi_lista()
{
    var a = [];
    var es = document.getElementsByTagName("*");
    for(var i = 0; i < es.length; i++)
    {
        if(es[i].id && es[i].id.substr(0, 6) == "lista_")
            a.push(es[i]);
    }
    return a;
}

// ]]>
</script>
</head>
<body>
    <input id="Button1" type="button" value="button" onclick="return Button1_onclick()" />

    <input type="text" id="lista_0" value="valore_0" />

    <input type="text" id="lista_1" value="valore_1" />

    <input type="text" id="lista_2" value="valore_2" />

    <input type="text" id="lista_3" value="valore_3" />

</body>
</html>