Avoid unnecessary parameter in URL

[eluser]Volkscom[/eluser]
In our site we have a function 'reg_new' in a controller 'registeration' without any parameter, but when we type anything after the url ie, www.ABCD.index.php/registeration/reg_new/bank.html, it show the basic registration page. But we need to show the home page/404 page instead of registration view page.
How can we do that?.