Re: pre-HTML5 and the BOM

From: Leif Halvard Silli <>
Date: Fri, 13 Jul 2012 15:12:04 +0200

Leif Halvard Silli, Fri, 13 Jul 2012 13:44:42 +0200:
> I do at least not think that user agents that
> want to be conforming pre-HTML5 user agents have any justification for
> ignoring the BOM.

* The effect of the BOM - as encoding signature - is not discussed
anywhere in HTML4 or in the 'text/html' MIME registration. We can say
that HTML4 is/became under-specified.

* The Appendix C of XHTML does not give any advice against including
BOM in the XHTML file, before serving it as 'text/html'.

* No pre-HTML5 browsers that I know, go into Quirks Mode because of the
BOM. (But - for that matter - quirks mode was not specced before HTML5

The kind of BOM intolerance I know about in user agents is that some
text browsers and IE5 for Mac (abandoned) "convert" the BOM into a
(typically empty) line a the start of the <body> element.

But since HTML4 was open-ended with regard to encodings - it did not
spec any specific encodings, HTML4 effectively said that encodings
could come and go, and eventually develop. So I think pre-HTML5
browsers for that reason can not legitimately behave as these BOM
intolerant browsers do.

Leif Halvard Silli
Received on Fri Jul 13 2012 - 08:16:03 CDT

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