Translated pages load a white empty page on localised site
I found this: 

I only copied the lines

// Path to your craft/ folder
$craftPath = '../../craft';

// Tell Craft to serve the German content
define('CRAFT_LOCALE', 'de');

// Do not edit below this line
// ...


from the example here: https://craftcms.com/docs/localization-guide to the index.php file in the localised folder.

I did not copy the $path lines from the original index.php file in the webroot. This way I got the white empty pages. 

Thanks a lot for the help on Twitter. I'm on my way to finish my first site!