Please post in the forum board pertaining to the template you are using with a url to where this can be seen so that we can address it from there.
I posted here because it is not template specific and I could not find a forum that would be appropriate for that. I have tried it in two templates -- corporate response and free vertex template. Both have this same behavior. I cannot send you to an URL since the site is still in development on my own local server. That's why I included screenshots.
But here... go to your own demo at http://www.shape5.com/demo/index.php?corporate_response
and click "Register" in the right hand breadcrumb area. Then click and drag the right-hand edge of the browser so it shrinks. As it approaches the limits of the size of the registration form, at some point you will see the edit fields overlap the boundaries of the area on the right side. They do not shrink appropriately. It's a minor glitch... just thought you would want to know in case it has further reaching implications on other devices.
Hope that is enough information to help.
EDIT: Sorry--I referenced the incorrect link above. Your online demo of the corporate template has a pop-up login. The free vertex template in the online demo exhibits the behavior I'm referring to. Use the link http://www.shape5.com/demo/index.php?vertex
. But both templates exhibit the behavior if the login/registration is a non pop-up.