#nav li {
display: inline; 
list-style:none;
}

#nav li a { 
float: left; 
display:inline; 
margin: 0;
}

#nav ul {margin:0;padding:0;}

#nav li a img {  border:none; vertical-align:bottom; /* for IE6 */}
#nav li a:hover { visibility:visible; }
#nav li a:hover img { visibility:visible; }

/**/ 
#nav li a:hover img {
visibility:hidden;
}

/* hide from IE5.0/win */

#one { background:url(img/btn/btn_quienes_over.jpg) no-repeat left top; }
#two { background:url(img/btn/btn_objetivos_over.jpg) no-repeat left top; }
#three { background:url(img/btn/btn_tecnicas_over.jpg) no-repeat left top; }
#four { background:url(img/btn/btn_contacto_over.jpg) no-repeat left top; }
#five { background:url(en/img-en/btn/btn_who_over.jpg) no-repeat left top; }
#six { background:url(en/img-en/btn/btn_objectives_over.jpg) no-repeat left top; }
#seven { background:url(en/img-en/btn/btn_tecnical_over.jpg) no-repeat left top; }
#eight { background:url(en/img-en/btn/btn_contact_over.jpg) no-repeat left top; }
#nine { background:url(pt/img-pt/btn/btn_quem_over.jpg) no-repeat left top; }
#ten { background:url(pt/img-pt/btn/btn_objetivos_over.jpg) no-repeat left top; }
#eleven { background:url(pt/img-pt/btn/btn_especificaciones-pt_over.jpg) no-repeat left top; }
#twelve { background:url(pt/img-pt/btn/btn_contato_over.jpg) no-repeat left top; }