Now there's a problem: I can't enter text into those fields. I made an empty HTML-file with just the form and it works. I have no idea what could be causing that.
I can access it via Tab and can click it so I can see the values I've entered in other fields. I can choose between the radio buttons by pressing the left/right arrow key. But I can't write or select the text or anything.
Yes, I saved it in a separate file (registration.php). If I open that file directly, it works like a charm, I can enter text as I like. But when this file is included or the code is written in the other file, I can't edit the content.
Something from my site must be blocking this, but I have no idea what.