Back in the day, when we had just entered a new millennium and Netscape was so my favourite browser, I had my very first HTML web-page-making bug.
It was all to do with <br> (not <br />), and the fact that if you put a <br> at the beginning of a new line, Netscape would play up and make it all look quite funny. I can’t remember the exacts of it, but I think the line height for the first line of the newly <br>‘d text was too low, so it was squashed (or perhaps the opposite).