thats why we tell posters to validate their markup and correct their errors and warnings.... Yahoo, Google site builder, Eric Myer, Max Designs all recommend that deviners should always validate their markup.
html5 is the first spec to specify how browsers should correct errors.
each browser vendor has their own interpretation of how they correct errors in markup ..... what a mess.
The problem is html is a markup language, not a programming language.... it is not compilied before it goes down the wire... but the same problems exist in programming languages... there are plenty of variants of C
junk in >> junk out