HTML and CSS Reference
In-Depth Information
It's very useful in overcoming a bug in Internet Explorer whereby,
under some circumstances, elements such as headings that were
targets of in-page links were never focused for screen reader
users, leaving the information inaccessible. (See www.juicystudio.
com/article/ie-keyboard-navigation.php for more information.) In
HTML 4, “-1” was an invalid value for the attribute, and the attri-
bute itself was invalid on any element other than form fi elds and
links. However, as it works in browsers now and it solves a real
problem, HTML5 legalises it everywhere. Yay!
Features not covered in this topic
For completeness, here are some of the most interesting
features of HTML5 that, for reasons of page count or lack of
implementation, aren't discussed further.
<embed> is well-known and has been used for years, but was
always an outlaw element that never validated. But like that
other outlaw, Robin Hood, it was widely supported because
it performed a useful function: It's the only way to get plug-ins
such as Flash to work reliably in all browsers, which explains
its overwhelmingly common usage (see 2008 stats at ). Because
of this, there's no reason to keep it from validating. HTML5
paves that particular cowpath and fi nally includes it into the
formal language specifi cation.
But hang on. Isn't HTML5 supposed to replace all these plug-in-
based technologies? Contrary to the black-and-white headlines
of some journalists, HTML5 won't magically replace plug-ins
overnight, and now we can embed them into HTML5 without
incurring the wrath of the validator.
This element, which is already well supported in all browsers
other than the big IE elephant in the room, is used in situ-
ations where your form needs to send a public key. If you
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