left aligned text is shown right alighned

I have a problem with generated Web help: Left aligned text in header is shown right aligned in Explorer (9, 10 and 11) with RH 11.

It puzzles me what has changed since RH9 where this never happened:

1) the header is set up in the Master page.

2) when generated the individual html page show it correctly when displayed in Explorer:

here seen as a topic

3) However when customers access the webhelp they see it right-aligned:

I'm baffeled and at my wits end. Help!