Erro 312 (net::ERR_UNSAFE_PORT)

I was using firefox to access a new Sharepoint site with a port number:

http://[url]:6000

then

"Erro 312 (net::ERR_UNSAFE_PORT): Erro desconhecido."

What a strange error, this only happen on Firefox and Chrome, IE works fine

The problem: Firefox and Chrome have security properties about ports diferent 80 and block access....

So how to override this situation,

After a litle search a College sugest me this solution, only work with Firefox,

On url write

"about:config"

click next

add new Property "String"

network.security.ports.banned.override

Then add the port Number:

6000

and now works like a charme....