Hola
ess_sebastian
Prueba este código:
Código PHP:
<html>
<head>
<script type="text/javascript">
function activar(frm) {
frm.enviar.disabled = (frm.txt1.value=='' || frm.txt2.value=='');
}
</script>
</head>
<body>
<form>
<input type="text" name="txt1" onkeyup="activar(this.form)" />
<input type="text" name="txt2" onkeyup="activar(this.form)" />
<input type="submit" name="enviar" disabled="disabled" />
</form>
</body>
</html>
Saludos,
