Creando un recuadro flotante centrado:


Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,Hola mundo, hola mundo, hola mundo, hola mundo,
Este es nuestro div centrado horizontalmente

* Atrás (Vólver al menú de Ejercicios de HTML/CSS).
* Ir al menú de ejercicios de JAVASCRIPT.

* Inicio de la web.