HTML and CSS Reference
In-Depth Information
— A
button
element cannot contain
a
,
form
,
input
,
select
,
textarea
,
label
,
button
,
iframe
, or
isindex
.
— The
label
element cannot contain other
label
elements.
▪ The special characters
<
,
>
,
&
,
'
, and
"
must always be represented by their character entit-
ies, including when they appear within attribute values. For example,
<
,
>
,
&
,
'
, and
"
(respectively).
▪ XHTML documents must use
id
instead of
name
for identifying document fragments and
in
a
,
applet
,
form
,
frame
,
iframe
,
img
, and
map
elements.
▪ XHTMLdocumentsshouldbeservedasXMLapplications,notasHTMLtextdocuments.
More specifically, the server should be configured to serve XHTML documents with the
Content-type header set to
application/xhtml+xml
. If it is not possible to configure the
server, the content type may be specified in a
meta
element in the document's
head
, as
shown in this example:
<meta http-equiv="content-type"
content="
application/xhtml+xml
; charset=UTF-8" />
Unfortunately, some popular browsers (Internet Explorer in particular) cannot parse
XHTML documents as XML, causing pages to break. For more information on XHTML
MIME types, see
www.w3.org/TR/xhtm-media-types/
.