When you hover your mouse over a paragraph of the Standard Edition (SE) long enough, the corresponding text from Gesammelte Werke slides from the bottom of the PEP-Web window, and vice versa.
If the slide up window bothers you, you can turn it off by checking the box “Turn off Translations” in the slide-up. But if you’ve turned it off, how do you turn it back on? The option to turn off the translations only is effective for the current session (it uses a stored cookie in your browser). So the easiest way to turn it back on again is to close your browser (all open windows), and reopen it.