I was working for a client on a simple landing page. After struggling for days with the text-flow of one paragraph and trying one CSS property after another I finally realized it.
He sent me the texts in PDF format and I just copied them. What I did not know is that all the spaces in the text were non breaking spaces wich of course did not wrap like I expected.

Heureka. You bloody bitch. Never imagined having such a fucking issue in web development...