On focus: moving focus to another control.

Load page and tab into the Email address text input. Try clicking with mouse inside the email text input. You will not be able to as the focus always gets passed to the password field.

On focus: changing experience with a link

Load the page and tab to the link

On focus: opening an alert (or new window) with a link

Tab to the link. A confirmation will open. A keyboard user will never be able to get to the "Can't reach me" button unless they answer Cancel in the dialog.