I created a child theme from twentythirteen and it worked like it should. Then I made a copy of the parent theme's header.php. As soon as I created it, the outputted HTML got broken. All tags that are supposed to go in the
<head>-tag instead shows up in the
<body>-tag, and the
<head> is empty. This happens even if the content of header.php in my child theme is exactly the same as the original.
The same happens if I create a new functions.php in my child theme. Even though it only contains this:
or is totally empty. If I remove the file, the head content get put in the correct place again.
EDIT: The actual source code is actually correct (if I choose "view source"), the error only shows up in inspector mode in Chrome and IE, but not in Firefox's inspector.