Artemis wrote:
I'm confused lol. My personal site is XHTML and I don't get any popup
box when viewing in IE.
That is because the MIME type sent in the HTTP Content-Type header would
be set to text/html. As has been discussed in this thread, the correct
MIME type is application/xhtml+xml, but because IE does not recognise
that, it offers the user the choice of what to do with the file (save or
open with another application).
What is this <?xml?> used for? Why would the average personal site need
it? If you could explain in "beginner speak", I would greatly appreciate
it :)
The XML declaration is supposed to be used to define the version of XML
being used (not to be confused with the actual markup language version
number, as in XHTML 1.0 or XHTML 1.1), the character encoding of the
file and whether or not the it's a standalone document (but I won't go
into the details about the standalone attribute, it's rarely needed).
The syntax looks like the following and, when present, must occur on the
first line of the file with no whitespace or other text before it
(except maybe a UTF-8, -16 or -32 Byte Order Mark (BOM))
<?xml version="1.0" encoding="UTF-8"?>
The version number refers to the XML version. There is currently only
XML 1.0 and XML 1.1. Most XML that people write (including XHTML,
MathML, SVG, etc.) is XML 1.0. There are significant differences
between 1.0 and 1.1, but I won't go into detail here. Basically, unless
you have a specific need to use XML 1.1, then use 1.0.
Be aware that an XML 1.0 parser that was not built for XML 1.1 as well,
will fail with a well-formedness error if version="1.1" is encountered
in the declaration. For XML 1.0, the XML declaration is optional.
The encoding determines the actual character encoding of the file. This
can be any encoding name you like, preferably one defined by IANA.
The encoding attribute may be omitted, and in the absence of such
information from a higher level protocol (e.g. the HTTP Content-Type
header), the default for XML is UTF-8 or UTF-16. XML user agents will
thus attempt to use either of those, determined by the presence or
absence of the BOM.
The BOM is a essentially special Unicode character (U+FEFF) used for
determining the particular UTF encoding, based on how the character
itself is actually encoded within the file.
There is also a standalone attribute that can be set to "yes" or "no",
but as I said I won't go into the details of what it means, it's quite
confusing and you normally just leave it out.
Lastly, it is important that the version and encoding attributes appear
in that specific order. It is not well-formed to write this:
<?xml encoding="UTF-8" version="1.0"?>
As I said, the encoding attribute may be omitted, if the encoding is
UTF-8 or UTF-16 (or if it is specified in a higher level protocol), so
this is well-formed:
<?xml version="1.0"?>
If you are using XHTML and serving it as text/html, it's best to leave
it out because anything before the DOCTYPE declaration will trigger
quirks mode in IE, which is basically a mode that uses intentionally
buggy, backwards compatible parsing and rendering behaviour reversed
engineered from obsolete 4.x era (and earlier) browsers.
--
Lachlan Hunt
http://lachy.id.au/
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