<s>
In	O
web	O
development	O
,	O
"	O
tag	B-General_Concept
soup	I-General_Concept
"	O
is	O
a	O
pejorative	O
for	O
syntactically	O
or	O
structurally	O
incorrect	O
HTML	B-Language
written	O
for	O
a	O
web	O
page	O
.	O
</s>
<s>
Because	O
web	B-Application
browsers	I-Application
have	O
historically	O
treated	O
structural	O
or	O
syntax	B-Application
errors	I-Application
in	O
HTML	B-Language
leniently	O
,	O
there	O
has	O
been	O
little	O
pressure	O
for	O
web	O
developers	O
to	O
follow	O
published	O
standards	O
,	O
and	O
therefore	O
there	O
is	O
a	O
need	O
for	O
all	O
browser	B-Application
implementations	O
to	O
provide	O
mechanisms	O
to	O
cope	O
with	O
the	O
appearance	O
of	O
"	O
tag	B-General_Concept
soup	I-General_Concept
"	O
,	O
accepting	O
and	O
correcting	O
for	O
invalid	B-Application
syntax	O
and	O
structure	O
where	O
possible	O
.	O
</s>
<s>
An	O
HTML	B-Language
parser	B-Language
(	O
part	O
of	O
a	O
web	B-Application
browser	I-Application
)	O
that	O
is	O
capable	O
of	O
interpreting	O
HTML-like	O
markup	O
even	O
if	O
it	O
contains	O
invalid	B-Application
syntax	O
or	O
structure	O
may	O
be	O
called	O
a	O
tag	B-General_Concept
soup	I-General_Concept
parser	B-Language
.	O
</s>
<s>
All	O
major	O
web	B-Application
browsers	I-Application
currently	O
have	O
a	O
tag	B-General_Concept
soup	I-General_Concept
parser	B-Language
for	O
interpreting	O
malformed	O
HTML	B-Language
,	O
with	O
most	O
error-handling	B-General_Concept
elements	O
standardized	O
.	O
</s>
<s>
"	O
Tag	B-General_Concept
soup	I-General_Concept
"	O
encompasses	O
many	O
common	O
authoring	O
mistakes	O
,	O
such	O
as	O
malformed	B-General_Concept
HTML	I-General_Concept
tags	I-General_Concept
,	O
improperly	O
nested	O
HTML	B-General_Concept
elements	I-General_Concept
,	O
and	O
unescaped	B-Algorithm
character	B-General_Concept
entities	I-General_Concept
(	O
especially	O
ampersands	O
(	O
)	O
and	O
less-than	O
signs	O
(	O
)	O
)	O
.	O
</s>
<s>
The	O
Markup	O
Validation	O
Service	O
is	O
a	O
resource	O
for	O
web	O
page	O
authors	O
to	O
avoid	O
creating	O
tag	B-General_Concept
soup	I-General_Concept
.	O
</s>
<s>
"	O
Tag	B-General_Concept
soup	I-General_Concept
"	O
is	O
a	O
term	O
used	O
to	O
denigrate	O
various	O
practices	O
in	O
web	O
authoring	O
.	O
</s>
<s>
Malformed	O
markup	O
where	O
tags	B-General_Concept
are	O
improperly	O
nested	O
or	O
incorrectly	O
closed	O
.	O
</s>
<s>
Invalid	B-Application
structure	O
where	O
elements	O
are	O
improperly	O
nested	O
according	O
to	O
the	O
DTD	B-Language
for	O
the	O
document	O
.	O
</s>
<s>
Examples	O
of	O
this	O
include	O
nesting	O
a	O
"	O
ul	O
"	O
element	O
directly	O
inside	O
another	O
"	O
ul	O
"	O
element	O
for	O
any	O
of	O
the	O
HTML	B-Language
4.01	I-Language
or	O
XHTML	B-Language
DTDs	O
.	O
</s>
<s>
For	O
example	O
the	O
use	O
of	O
the	O
Blink	B-Application
element	I-Application
or	O
the	O
Marquee	B-General_Concept
element	I-General_Concept
which	O
were	O
non-standard	O
elements	O
originally	O
only	O
supported	O
by	O
Netscape	B-Protocol
and	O
Internet	B-Application
Explorer	I-Application
browsers	B-Application
respectively	O
.	O
</s>
<s>
However	O
,	O
thanks	O
to	O
better	O
education	O
and	O
information	O
and	O
perhaps	O
with	O
some	O
help	O
from	O
XHTML	B-Language
,	O
the	O
issue	O
of	O
malformed	O
markup	O
is	O
becoming	O
less	O
common	O
.	O
</s>
<s>
Browsers	B-Application
,	O
when	O
faced	O
with	O
malformed	O
markup	O
,	O
must	O
guess	O
the	O
intended	O
meaning	O
of	O
the	O
author	O
.	O
</s>
<s>
They	O
must	O
infer	O
closing	O
tags	B-General_Concept
where	O
they	O
expect	O
them	O
and	O
then	O
infer	O
opening	O
tags	B-General_Concept
to	O
match	O
other	O
closing-tags	O
.	O
</s>
<s>
The	O
interpretation	O
can	O
vary	O
markedly	O
from	O
one	O
browser	B-Application
to	O
the	O
next	O
.	O
</s>
<s>
While	O
many	O
graphical	O
web	O
editors	O
produce	O
well-formed	O
markup	O
,	O
an	O
author	O
writing	O
code	O
manually	O
with	O
a	O
text-editor	O
and	O
then	O
testing	O
only	O
in	O
one	O
browser	B-Application
can	O
easily	O
miss	O
such	O
errors	O
.	O
</s>
<s>
The	O
presentation	O
can	O
therefore	O
vary	O
drastically	O
from	O
one	O
browser	B-Application
to	O
another	O
as	O
each	O
tries	O
to	O
"	O
correct	O
"	O
the	O
authorʼs	O
intent	O
in	O
different	O
ways	O
and	O
then	O
applies	O
styling	O
to	O
those	O
"	O
corrections	O
"	O
.	O
</s>
<s>
Invalid	B-Application
document	O
structure	O
here	O
means	O
only	O
the	O
use	O
of	O
attributes	O
and	O
elements	O
where	O
they	O
do	O
not	O
belong	O
.	O
</s>
<s>
For	O
example	O
,	O
placing	O
a	O
"	O
cite	O
"	O
attribute	O
on	O
a	O
"	O
cite	O
"	O
element	O
is	O
invalid	B-Application
since	O
the	O
HTML	B-Language
and	O
XHTML	B-Language
DTDs	O
do	O
not	O
ascribe	O
any	O
meaning	O
to	O
that	O
attribute	O
on	O
that	O
element	O
.	O
</s>
<s>
Similarly	O
,	O
including	O
a	O
"	O
p	O
"	O
element	O
within	O
the	O
content	O
of	O
an	O
"	O
em	O
"	O
element	O
is	O
also	O
invalid	B-Application
.	O
</s>
<s>
With	O
the	O
move	O
toward	O
separating	O
malformed	O
markup	O
from	O
invalid	B-Application
markup	O
,	O
the	O
problems	O
with	O
invalid	B-Application
markup	O
have	O
increasingly	O
been	O
seen	O
as	O
less	O
severe	O
.	O
</s>
<s>
Some	O
have	O
begun	O
to	O
advocate	O
looser	O
content	O
models	O
that	O
allow	O
greater	O
flexibility	O
in	O
authoring	O
HTML	B-Language
documents	O
(	O
whether	O
in	O
HTML	B-Language
or	O
XHTML	B-Language
)	O
.	O
</s>
<s>
However	O
,	O
use	O
of	O
invalid	B-Application
markup	O
can	O
blur	O
the	O
author	O
's	O
intended	O
meaning	O
,	O
though	O
not	O
as	O
severely	O
as	O
malformed	O
markup	O
.	O
</s>
<s>
Many	O
graphic	O
web	O
editors	O
still	O
produce	O
invalid	B-Application
markup	O
.	O
</s>
<s>
It	O
is	O
common	O
to	O
see	O
invalid	B-Application
markup	O
in	O
many	O
of	O
the	O
sites	O
throughout	O
the	O
World	O
Wide	O
Web	O
.	O
</s>
<s>
In	O
the	O
early	O
age	O
of	O
the	O
web	O
(	O
much	O
of	O
the	O
1990s	O
)	O
,	O
the	O
design	O
of	O
the	O
official	O
HTML	B-Language
specification	O
became	O
increasingly	O
strained	O
,	O
compared	O
to	O
the	O
desire	O
of	O
designers	O
for	O
flexibility	O
in	O
creating	O
visually	O
vibrant	O
designs	O
.	O
</s>
<s>
In	O
response	O
to	O
this	O
pressure	O
,	O
browser	B-Application
makers	O
unilaterally	O
added	O
new	O
proprietary	O
features	O
to	O
HTML	B-Language
that	O
fell	O
outside	O
the	O
standards	O
at	O
the	O
time	O
.	O
</s>
<s>
This	O
meant	O
there	O
were	O
proprietary	O
elements	O
in	O
HTML	B-Language
that	O
worked	O
in	O
some	O
browsers	B-Application
,	O
but	O
not	O
in	O
others	O
.	O
</s>
<s>
To	O
some	O
extent	O
,	O
this	O
problem	O
was	O
slowed	O
by	O
the	O
introduction	O
of	O
new	O
standards	O
by	O
the	O
W3C	O
,	O
such	O
as	O
CSS	B-Language
,	O
introduced	O
in	O
1998	O
,	O
which	O
helped	O
to	O
provide	O
greater	O
flexibility	O
in	O
the	O
presentation	O
and	O
layout	O
of	O
web	O
pages	O
without	O
the	O
need	O
for	O
large	O
numbers	O
of	O
additional	O
HTML	B-General_Concept
elements	I-General_Concept
and	O
attributes	O
.	O
</s>
<s>
Moreover	O
,	O
in	O
HTML	B-Language
4	O
and	O
XHTML	B-Language
1	O
,	O
many	O
elements	O
were	O
either	O
superseded	O
by	O
a	O
single	O
semantic	O
construct	O
(	O
such	O
as	O
object	O
elements	O
replacing	O
proprietary	O
applet	O
and	O
embed	O
elements	O
)	O
or	O
deprecated	O
due	O
to	O
being	O
presentational	O
(	O
such	O
as	O
the	O
"	O
s	O
"	O
,	O
"	O
strike	O
"	O
and	O
"	O
u	O
"	O
elements	O
)	O
.	O
</s>
<s>
Nevertheless	O
,	O
browser	B-Application
developers	O
continued	O
to	O
introduce	O
new	O
elements	O
to	O
HTML	B-Language
when	O
they	O
perceived	O
a	O
need	O
.	O
</s>
<s>
Some	O
browsers	B-Application
included	O
tabindex	O
attributes	O
on	O
any	O
element	O
.	O
</s>
<s>
Developers	O
of	O
Apple	O
's	O
WebKit	B-Language
introduced	O
the	O
canvas	B-Language
element	I-Language
,	O
a	O
version	O
of	O
which	O
was	O
subsequently	O
adopted	O
by	O
Mozilla	B-Operating_System
.	O
</s>
<s>
In	O
2004	O
,	O
Apple	O
,	O
Mozilla	B-Operating_System
and	O
Opera	O
founded	O
the	O
WHATWG	B-Language
,	O
with	O
the	O
intent	O
of	O
creating	O
a	O
new	O
version	O
of	O
the	O
HTML	B-Language
specification	O
which	O
all	O
browser	B-Application
behavior	O
would	O
match	O
.	O
</s>
<s>
This	O
included	O
changing	O
the	O
specification	O
if	O
necessary	O
to	O
match	O
an	O
existing	O
consensus	O
between	O
different	O
browsers	B-Application
.	O
</s>
<s>
The	O
canvas	B-Language
and	O
embed	O
elements	O
were	O
subsequently	O
standardised	O
by	O
the	O
WHATWG	B-Language
.	O
</s>
<s>
Versions	O
of	O
the	O
WHATWG	B-Language
specification	O
were	O
published	O
by	O
the	O
W3C	O
as	O
HTML5	B-Application
.	O
</s>
<s>
While	O
some	O
of	O
the	O
issues	O
of	O
tag	B-General_Concept
soup	I-General_Concept
are	O
due	O
to	O
shortcomings	O
of	O
browsers	B-Application
and	O
sometimes	O
due	O
to	O
a	O
lack	O
of	O
information	O
for	O
web	O
authors	O
,	O
some	O
of	O
the	O
proliferation	O
of	O
tag	B-General_Concept
soup	I-General_Concept
was	O
due	O
to	O
missing	O
links	O
in	O
the	O
web	O
standards	O
themselves	O
.	O
</s>
<s>
As	O
more	O
browsers	B-Application
support	O
newer	O
revisions	O
of	O
standards	O
,	O
the	O
pressure	O
on	O
web	O
developers	O
to	O
use	O
non-standard	O
code	O
to	O
solve	O
problems	O
diminishes	O
.	O
</s>
<s>
Cascading	B-Language
Style	I-Language
Sheets	I-Language
(	O
CSS	B-Language
)	O
provide	O
a	O
mechanism	O
to	O
specify	O
the	O
presentation	O
of	O
elements	O
in	O
a	O
document	O
without	O
altering	O
the	O
markup	O
structure	O
of	O
the	O
document	O
.	O
</s>
<s>
Before	O
CSS	B-Language
was	O
commonplace	O
,	O
web	O
developers	O
may	O
have	O
resorted	O
to	O
some	O
structurally	O
invalid	B-Application
markup	O
to	O
achieve	O
certain	O
presentational	O
goals	O
–	O
for	O
example	O
,	O
including	O
block	B-General_Concept
level	I-General_Concept
elements	I-General_Concept
within	O
inline	O
elements	O
to	O
obtain	O
a	O
particular	O
effect	O
,	O
or	O
using	O
sometimes	O
large	O
numbers	O
of	O
<font>	O
and	O
other	O
display-specific	O
HTML	B-General_Concept
tags	I-General_Concept
.	O
</s>
<s>
CSS	B-Language
uses	O
style	O
rules	O
to	O
accomplish	O
these	O
tasks	O
while	O
leaving	O
the	O
markup	O
cleaner	O
and	O
simpler	O
.	O
</s>
<s>
XHTML	B-Language
is	O
a	O
reformulation	O
of	O
the	O
HTML	B-Language
language	I-Language
based	O
on	O
XML	B-Protocol
.	O
</s>
<s>
XHTML	B-Language
was	O
developed	O
to	O
address	O
many	O
of	O
the	O
problems	O
associated	O
with	O
tag	B-General_Concept
soup	I-General_Concept
.	O
</s>
<s>
XML	B-Protocol
allows	O
parsers	B-Language
to	O
separate	O
the	O
process	O
of	O
interpreting	O
the	O
document	O
syntax	O
and	O
its	O
structure	O
.	O
</s>
<s>
In	O
HTML	B-Language
and	O
SGML	B-Language
,	O
a	O
parser	B-Language
needed	O
to	O
know	O
certain	O
rules	O
about	O
elements	O
during	O
parsing	O
,	O
such	O
as	O
what	O
elements	O
could	O
be	O
contained	O
within	O
other	O
elements	O
and	O
which	O
elements	O
implicitly	O
close	O
the	O
previous	O
element	O
.	O
</s>
<s>
This	O
is	O
because	O
in	O
HTML	B-Language
and	O
SGML	B-Language
,	O
closing	O
tags	B-General_Concept
and	O
even	O
opening	O
tags	B-General_Concept
were	O
optional	O
on	O
some	O
elements	O
.	O
</s>
<s>
By	O
requiring	O
all	O
elements	O
to	O
have	O
explicit	O
opening	O
and	O
closing	O
tags	B-General_Concept
,	O
XML	B-Protocol
parsers	I-Protocol
can	O
parse	O
the	O
document	O
and	O
produce	O
a	O
document	O
tree	O
without	O
any	O
knowledge	O
of	O
the	O
document	O
type	O
.	O
</s>
<s>
This	O
allows	O
parsers	B-Language
to	O
be	O
universal	O
and	O
very	O
light-weight	O
,	O
and	O
to	O
be	O
separated	O
from	O
the	O
process	O
of	O
validating	O
or	O
interpreting	O
the	O
document	O
.	O
</s>
<s>
The	O
XML	B-Protocol
specification	I-Protocol
clearly	O
defines	O
that	O
a	O
conforming	O
user	O
agent	O
(	O
such	O
as	O
a	O
web	B-Application
browser	I-Application
)	O
must	O
not	O
accept	O
a	O
document	O
,	O
and	O
not	O
continue	O
parsing	O
it	O
,	O
if	O
any	O
syntactical	O
error	O
is	O
encountered	O
.	O
</s>
<s>
Thus	O
,	O
a	O
browser	B-Application
interpreting	O
a	O
web	O
page	O
as	O
XHTML	B-Language
will	O
refuse	O
to	O
display	O
the	O
page	O
if	O
it	O
encounters	O
a	O
formation	O
error	O
.	O
</s>
<s>
This	O
can	O
help	O
ensure	O
that	O
when	O
authors	O
test	O
XHTML	B-Language
code	O
against	O
a	O
conforming	O
browser	B-Application
they	O
will	O
immediately	O
be	O
informed	O
of	O
malformation	O
problems	O
:	O
perhaps	O
the	O
most	O
severe	O
problem	O
facing	O
web	B-Application
browsers	I-Application
.	O
</s>
<s>
Without	O
the	O
directives	O
of	O
XML	B-Protocol
,	O
HTML	B-Language
browsers	B-Application
must	O
use	O
complex	O
algorithms	O
to	O
infer	O
the	O
author	O
's	O
intended	O
meaning	O
in	O
a	O
wide	O
range	O
of	O
cases	O
where	O
invalid	B-Application
syntax	O
is	O
encountered	O
.	O
</s>
<s>
XML	B-Protocol
and	O
XHTML	B-Language
introduce	O
the	O
concept	O
of	O
namespaces	O
.	O
</s>
<s>
With	O
namespaces	O
,	O
authors	O
or	O
communities	O
of	O
authors	O
can	O
define	O
new	O
elements	O
and	O
attributes	O
with	O
new	O
semantics	O
,	O
and	O
intermix	O
those	O
within	O
their	O
XHTML	B-Language
documents	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
"	O
table	O
"	O
element	O
could	O
be	O
defined	O
in	O
a	O
new	O
namespace	O
with	O
new	O
semantics	O
different	O
from	O
the	O
HTML	B-Language
"	O
table	O
"	O
element	O
and	O
the	O
browser	B-Application
will	O
be	O
able	O
to	O
differentiate	O
between	O
the	O
two	O
.	O
</s>
<s>
In	O
providing	O
namespaces	O
,	O
XHTML	B-Language
combined	O
with	O
CSS	B-Language
allow	O
authoring	O
communities	O
to	O
easily	O
extend	O
the	O
semantic	O
vocabulary	O
of	O
documents	O
.	O
</s>
<s>
XHTML	B-Language
documents	O
may	O
be	O
served	O
on	O
the	O
web	O
using	O
the	O
internet	B-Application
media	I-Application
type	I-Application
application/xhtml	O
+xml	O
or	O
text/html	B-Language
Microsoft	B-Application
Internet	I-Application
Explorer	I-Application
versions	O
before	O
9	B-Application
do	O
not	O
display	O
XHTML	B-Language
documents	O
served	O
as	O
application/xhtml	O
+xml	O
.	O
</s>
<s>
IE9	B-Application
and	O
later	O
versions	O
are	O
compliant	O
.	O
</s>
<s>
See	O
also	O
the	O
discussion	O
of	O
this	O
issue	O
in	O
the	O
XHTML	B-Language
article	O
.	O
</s>
<s>
HTML5	B-Application
aims	O
to	O
be	O
the	O
most	O
complete	O
solution	O
to	O
the	O
problem	O
of	O
tag	B-General_Concept
soup	I-General_Concept
thus	O
far	O
while	O
remaining	O
as	O
backwards	O
-	O
and	O
forwards-compatible	O
as	O
possible	O
.	O
</s>
<s>
By	O
contrast	O
to	O
XHTML	B-Language
,	O
which	O
departs	O
from	O
backwards	O
compatibility	O
and	O
takes	O
the	O
approach	O
that	O
parsers	B-Language
should	O
become	O
less	O
tolerant	O
of	O
badly	O
formed	O
markup	O
,	O
HTML5	B-Application
acknowledges	O
that	O
badly	O
formed	O
HTML	B-Language
code	I-Language
already	O
exists	O
in	O
large	O
quantities	O
and	O
will	O
probably	O
continue	O
to	O
be	O
used	O
,	O
and	O
takes	O
the	O
view	O
that	O
the	O
specification	O
should	O
be	O
expanded	O
to	O
ensure	O
maximum	O
compatibility	O
with	O
such	O
code	O
.	O
</s>
<s>
Thus	O
,	O
the	O
HTML	B-Application
5	I-Application
specification	O
has	O
altered	O
its	O
definition	O
of	O
HTML	B-Language
syntax	I-Language
both	O
to	O
accommodate	O
common	O
syntax	O
in	O
use	O
today	O
,	O
and	O
to	O
explicitly	O
describe	O
exactly	O
how	O
"	O
badly	O
formed	O
code	O
"	O
should	O
be	O
treated	O
by	O
the	O
parser	B-Language
.	O
</s>
<s>
The	O
handling	O
of	O
badly	O
formed	O
code	O
now	O
has	O
a	O
place	O
in	O
the	O
specification	O
itself	O
,	O
hopefully	O
reducing	O
the	O
need	O
for	O
future	O
HTML	B-Language
parsers	B-Language
to	O
implement	O
additional	O
,	O
out-of-specification	O
measures	O
for	O
dealing	O
with	O
code	O
that	O
it	O
does	O
not	O
recognize	O
.	O
</s>
<s>
HTML	B-Language
Tidy	I-Language
is	O
a	O
software	O
tool	O
available	O
for	O
many	O
platforms	O
which	O
can	O
correct	O
invalid	B-Application
syntax	O
,	O
and	O
most	O
invalid	B-Application
document	O
structure	O
,	O
converting	O
HTML-like	O
code	O
to	O
HTML	B-Language
or	O
XHTML	B-Language
.	O
</s>
<s>
is	O
a	O
Java	O
library	O
that	O
parses	O
HTML	B-Language
,	O
cleans	O
it	O
up	O
,	O
and	O
delivers	O
a	O
stream	O
of	O
SAX	B-Application
events	O
representing	O
well-formed	O
XML	B-Protocol
(	O
not	O
necessarily	O
valid	O
XHTML	B-Language
)	O
.	O
</s>
<s>
This	O
tools	O
is	O
used	O
for	O
processing	O
JNLP	O
files	O
in	O
the	O
open	O
source	O
implementation	O
of	O
the	O
JNLP	O
protocol	O
available	O
in	O
IcedTea-Web	O
,	O
a	O
sub-project	O
of	O
IcedTea	B-Language
,	O
the	O
build	O
and	O
integration	O
project	O
of	O
the	O
OpenJDK	B-Language
.	O
</s>
<s>
is	O
a	O
Python	O
DOM-like	O
parser	B-Language
for	O
soupy	O
HTML/XML	O
.	O
</s>
<s>
:	O
a	O
library	O
for	O
Haskell	B-Language
language	I-Language
.	O
</s>
<s>
Unlike	O
the	O
strict	O
XHTML	B-Language
,	O
HTML	B-Language
and	O
its	O
predecessor	O
SGML	B-Language
are	O
designed	O
to	O
be	O
written	O
by	O
humans	O
,	O
and	O
already	O
have	O
a	O
significant	O
degree	O
of	O
flexibility	O
in	O
syntax	O
to	O
reduce	O
boilerplate	O
.	O
</s>
<s>
These	O
differences	O
do	O
not	O
make	O
the	O
document	O
invalid	B-Application
and	O
are	O
therefore	O
not	O
tag	B-General_Concept
soup	I-General_Concept
.	O
</s>
<s>
The	O
following	O
apply	O
to	O
both	O
HTML	B-Language
4	O
and	O
HTML5	B-Application
,	O
and	O
examples	O
date	O
back	O
to	O
the	O
first	O
days	O
of	O
HTML	B-Language
.	O
</s>
<s>
Tags	B-General_Concept
like	O
can	O
often	O
be	O
omitted	O
completely	O
.	O
</s>
<s>
The	O
closure	O
of	O
tags	B-General_Concept
can	O
often	O
be	O
omitted	O
because	O
the	O
specification	O
rejects	O
some	O
elements	O
nesting	O
into	O
itself	O
.	O
</s>
<s>
Despite	O
their	O
validity	O
,	O
these	O
omissions	O
still	O
require	O
a	O
special	O
parser	B-Language
with	O
a	O
knowledge	O
of	O
HTML	B-Language
(	O
as	O
opposed	O
to	O
the	O
more	O
rigid	O
XML	B-Protocol
)	O
to	O
parse	O
.	O
</s>
<s>
For	O
example	O
,	O
HTML	B-Language
Tidy	I-Language
allows	O
omitting	O
optional	O
tags	B-General_Concept
,	O
but	O
defaults	O
to	O
not	O
doing	O
so	O
.	O
</s>
