I tried using that feature in DNN 5.2, by adding the text I wanted removed to the value = "" and it didn't work well at all.  I had proper portal alias's entered as well.

I'd recommend just adding a portal alias for www.midominio.com in Dotnetnuke, and then change your web host settings so your domain name is pointing to the "dnn" directory, for example in IIS you would set the "path" to point to "/dnn".  That always works well for me. 

Maybe someone with a better experience with the host header function in the web.config could give advice on how to actually use that function successfully, otherwise I'd use the method above. 

JOHN GIESY
DotNetNuke Hosting Expert

DotNetNuke 7 Hosting $70 /year
DNN4Less.com Team DotNetNuke  

Logged in as "host" and in "edit" mode, you will have access to add another portal alias.

If you don't have access to the IIS setup on your host, you should have access to the domain name settings and the directory the domain name points to.  If you don't have access to that either, you should be able to ask tech support at the web host to set the domain to point to the /dnn/ directory as the root for the domain name.  If they won't do it for you, then it's time to find a new web host, good tech support will always help you with that type of thing.  Especially helpful tech support can be found at WebHost4Life and 3Essentials, but I think both of those would allow you access to the IIS path settings at the very least, too.

Maybe someone will be able to help you with the host header function which may be easier in your case.

JOHN GIESY
DotNetNuke Hosting Expert

DotNetNuke 7 Hosting $70 /year
DNN4Less.com Team DotNetNuke