vincenzo.dellamea@gmail.com writes:
> At present, I have put a Redirect / http://www.site2.com/site1/
> directive on .htaccess. However, the browser then shows a
> http://www.site2.com/site1 URI, wilst I would rather prefer that the
> original www.site1.com URL remains.
> Is there any possibility to have this using rewriting?

No not really. The two ways to do it are with proxying or with an
HTML frame to disguise the page's real origin. The frame approach is
annoying and I hate sites that do it, but it's common. Depending on
the application it may be better to use a chromeless pop-up or
something.