creo que podría ser así:
Cita: <html> <head> <meta http-equiv="content-type" content="text/html;charset=utf-8" /> <title>Untitled Page</title> <script language="JavaScript"> function mostrar(campo){ if (campo.value!=""){ document.forms['form1']['submit'].style.visibility="visible"; }else{ document.forms['form1']['submit'].style.visibility="hidden"; } } </script> </head> <body> <form name="form1" method="post" action=""><input type="text" name="textfield" onkeyup="mostrar(this)"><br><input type="text" name="textfield2" onkeyup="mostrar(this)"> <br><input type="submit" name="submit" value="Submit" style="visibility:hidden"> </form> </body> </html>
chau
pd: probado en IE , opera y firefox