Código HTML:
<form id="form1" name="form1" method="post" action="lapaginaquesea.php" target="'popup' window.open('', 'popup', 'tolbar=0, width=500, height=520')" onsubmit="return validate(this);"> <br /> <input type="text" name="domain" size="10" /> <input type="hidden" name="action" value="whois"> <input type="hidden" name="show" value="1"> <select name="ext"> <option value=".com">.com</option> <option value=".net">.net</option> <option value=".info">.info</option> <option value=".org">.org</option> <option value=".biz">.biz</option> </select> <input type="submit" name="Submit" value="Buscar" />