Salve a tutti
dovrei realizzare un semplice form, dove i campi posso essere, a seconda della necessita' 1 sotto l'altro, in 2 colonne o in 3 colonne. Per fare questo ho realizzato la seguente pagina:

Codice PHP:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="it" lang="it" dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta name="MSSmartTagsPreventParsing" content="TRUE" />
    <title></title>

    <style>
    form fieldset{
        text-align:left;
        border:1px solid #CCC;
        padding: 15px;
        margin: 0 auto;
        width: 600px;
    }
    .content{
        padding: 1em 1em;
        background-color: #FFFFFF;
    }
    .center{
        margin: 0 auto;
        text-align:center;
    }
    
    .col1_3 {
        float:left;
        display: block;
        margin:0pt;
        width:100px;
    }
    .col2_3 {
        float:left;
        display: block;
        margin:0pt;
        width:250px;
    }
    .col3_3 {
        float:left;
        display: block;
        margin:0pt;
        width:235px;
    }
    </style>
</head>
<body bgcolor="white">
    <div class="content">
        <div class="center"> 
            <form name="form1" method="post" action="#">
                <fieldset>
                    <label> prova 1</label>
                    
                    <div class="col1_3">
                        <label>prova col1</label>
                    </div>
                    <div class="col2_3">
                        <label>prova col2</label>
                    </div>
                    <div class="col3_3">
                        <label>prova col3</label>

                    </div>
                    
                    <div class="col1_3">
                        <input name="c1" type="text" id="zip" size="9" maxlength="9" value=""/>
                    </div>
                    <div class="col2_3">
                        <input name="c2" type="text" id="city" size="35" maxlength="35" value=""/>
                    </div>
                    <div class="col3_3">
                        <input name="c3" type="text" id="state" size="2" maxlength="2" value=""/>
                    </div>
                    
                    <label>prova prova prova</label>
                </fieldset>
            </form>    
        <div>
    </div>
</body>
</html> 
ma, come potete vedere il risultato e' abbastanza strano: l'ultima label fuori dai div "col" si va ad unire alla prima e ho paura che il width delle colonne non vada bene per ie...
Potreste darmi un aiutino per risolvere i problemi?

grazie a tutti