I think ysleepy might be referring to HTML charsets, which can be set in the HTTP header. They are a nightmare, I have come across HTML documents with so many “

I think ysleepy might be referring to HTML charsets, which can be set in the HTTP header. They are a nightmare, I have come across HTML documents with so many “if lt IE 9” comments that they move the charset declaration out of the first 1000 bytes, causing browsers to ignore it and interpret as Latin 1. But yes, not actually anything to do with parsing HTTP.