<p>Is there a better way to keep the domain name unaltered in the adress bar besides using a main frame?</p>

You can use AJAX to change the content of the page without changing the address.
However, if the data is located on another domain then the address should change to point to that domain.  Also, it is recommended that the address can be bookmarked so user's can easily return to the data.  The address should reflect the content of the resource it points to.