<s>
Mozilla	B-Application
Firefox	I-Application
4	I-Application
is	O
a	O
version	O
of	O
the	O
Firefox	B-Application
web	I-Application
browser	I-Application
,	O
released	O
on	O
March	O
22	O
,	O
2011	O
.	O
</s>
<s>
It	O
was	O
codenamed	O
Tumucumaque	O
,	O
and	O
was	O
Firefox	B-Application
's	O
last	O
large	O
release	O
cycle	O
.	O
</s>
<s>
The	O
Mozilla	B-Operating_System
team	O
planned	O
smaller	O
and	O
quicker	O
releases	O
following	O
other	O
browser	B-Application
vendors	O
.	O
</s>
<s>
The	O
primary	O
goals	O
for	O
this	O
version	O
included	O
improvements	O
in	O
performance	O
,	O
standards	O
support	O
,	O
and	O
user	B-Application
interface	I-Application
.	O
</s>
<s>
There	O
was	O
one	O
security	O
update	O
in	O
April	O
2011	O
(	O
4.0.1	O
)	O
and	O
version	O
4	O
of	O
the	O
browser	B-Application
was	O
made	O
obsolete	O
by	O
the	O
release	O
of	O
Firefox	B-Application
5	O
in	O
June	O
2011	O
.	O
</s>
<s>
This	O
marked	O
a	O
transition	O
to	O
giving	O
much	O
less	O
weight	O
to	O
major	O
version	O
numbers	O
,	O
with	O
5	O
more	O
major	O
version	O
numbers	O
used	O
by	O
December	O
of	O
that	O
year	O
(	O
5	O
,	O
6	O
,	O
7	O
,	O
8	O
,	O
and	O
9	O
)	O
,	O
compared	O
to	O
4	O
in	O
nearly	O
a	O
decade	O
of	O
Firefox	B-Application
development	O
(	O
1	O
,	O
2	O
,	O
3	O
,	O
4	O
)	O
.	O
</s>
<s>
On	O
October	O
13	O
,	O
2006	O
,	O
Brendan	O
Eich	O
,	O
Mozilla	B-Operating_System
's	O
Chief	O
Technology	O
Officer	O
,	O
wrote	O
about	O
the	O
plans	O
for	O
"	O
Mozilla	B-Operating_System
2	O
"	O
,	O
referring	O
to	O
the	O
most	O
comprehensive	O
iteration	O
since	O
its	O
creation	O
of	O
the	O
overall	O
platform	O
on	O
which	O
Firefox	B-Application
and	O
other	O
Mozilla	B-Operating_System
products	O
run	O
.	O
</s>
<s>
The	O
largest	O
changes	O
,	O
however	O
,	O
were	O
deferred	O
to	O
Firefox	B-Application
4.0	I-Application
.	O
</s>
<s>
In	O
early	O
May	O
2010	O
,	O
Mozilla	B-Operating_System
's	O
plans	O
for	O
Firefox	B-Application
4.0	I-Application
were	O
officially	O
detailed	O
through	O
a	O
blog	O
post	O
by	O
Mike	O
Beltzner	O
,	O
Firefox	B-Application
director	O
.	O
</s>
<s>
On	O
May	O
25	O
,	O
2011	O
,	O
the	O
Firefox	B-Application
release	O
manager	O
wrote	O
in	O
an	O
email	O
"	O
Firefox	B-Application
5	O
will	O
be	O
the	O
security	O
update	O
for	O
Firefox	B-Application
4	I-Application
,	O
"	O
confirming	O
Firefox	B-Application
4	I-Application
had	O
entered	O
its	O
"	O
end	O
of	O
life	O
"	O
phase	O
where	O
Mozilla	B-Operating_System
will	O
no	O
longer	O
issue	O
updates	O
.	O
</s>
<s>
Mozilla	B-Operating_System
continued	O
to	O
issue	O
updates	O
for	O
Firefox	B-Protocol
3.6	I-Protocol
after	O
4	O
's	O
EOL	O
declaration	O
.	O
</s>
<s>
Only	O
one	O
update	O
(	O
4.0.1	O
)	O
was	O
issued	O
for	O
Firefox	B-Application
4	I-Application
during	O
its	O
lifetime	O
.	O
</s>
<s>
Mozilla	B-Application
Firefox	I-Application
4	I-Application
includes	O
many	O
new	O
features	O
since	O
version	B-Protocol
3.6	I-Protocol
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
brought	O
a	O
new	O
user	B-Application
interface	I-Application
,	O
with	O
a	O
new	O
look	O
designed	O
to	O
make	O
it	O
faster	O
.	O
</s>
<s>
Early	O
mockups	O
of	O
the	O
new	O
interface	O
on	O
Windows	B-Application
,	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
and	O
Linux	B-Application
were	O
first	O
made	O
available	O
in	O
July	O
2009	O
.	O
</s>
<s>
New	O
features	O
included	O
improved	O
"	O
doorhanger	O
"	O
notifications	O
,	O
Firefox	B-Application
Panorama	O
(	O
a	O
feature	O
that	O
lets	O
the	O
user	O
visually	O
group	O
tabs	O
)	O
,	O
application	O
tabs	O
,	O
a	O
redesigned	O
extension	O
manager	O
,	O
Jetpack	B-Application
extensions	O
support	O
,	O
integration	O
with	O
Firefox	B-Operating_System
Sync	I-Operating_System
,	O
and	O
support	O
for	O
multitouch	B-Application
displays	O
.	O
</s>
<s>
Many	O
changes	O
were	O
made	O
to	O
the	O
user	B-Application
interface	I-Application
.	O
</s>
<s>
On	O
Windows	B-Application
Vista	I-Application
and	O
Windows	B-Device
7	I-Device
,	O
the	O
menu	O
bar	O
is	O
hidden	O
by	O
default	O
with	O
the	O
most	O
common	O
actions	O
moved	O
to	O
a	O
new	O
"	O
Firefox	B-Application
"	O
menu	O
in	O
the	O
upper	O
left-hand	O
corner	O
of	O
the	O
browser	B-Application
.	O
</s>
<s>
Many	O
of	O
these	O
features	O
are	O
similar	O
to	O
ones	O
introduced	O
by	O
Google	B-Application
Chrome	I-Application
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
is	O
based	O
on	O
the	O
Gecko	B-Language
2.0	O
engine	O
,	O
which	O
adds	O
and	O
improves	O
support	O
for	O
HTML5	B-Application
,	O
CSS3	O
,	O
WebM	B-Application
,	O
and	O
WebGL	B-Library
.	O
</s>
<s>
Also	O
,	O
it	O
includes	O
a	O
new	O
JavaScript	B-Language
engine	I-Language
(	O
JägerMonkey	O
)	O
and	O
better	O
XPCOM	B-Application
APIs	B-General_Concept
.	O
</s>
<s>
JägerMonkey	O
is	O
a	O
new	O
JavaScript	B-Language
engine	I-Language
designed	O
to	O
work	O
alongside	O
the	O
TraceMonkey	O
engine	O
introduced	O
with	O
Firefox	O
3.5	O
.	O
</s>
<s>
It	O
improves	O
performance	O
by	O
compiling	O
"	O
non-traceable	O
"	O
JavaScript	B-Language
into	O
machine	O
language	O
for	O
faster	O
execution	O
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
is	O
the	O
first	O
version	O
of	O
Firefox	B-Application
to	O
drop	O
native	O
support	O
of	O
the	O
Gopher	B-Protocol
protocol	I-Protocol
;	O
however	O
,	O
continued	O
support	O
is	O
available	O
through	O
an	O
add-on	B-Operating_System
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
introduces	O
an	O
audio	O
API	B-General_Concept
,	O
which	O
provides	O
a	O
way	O
to	O
programmatically	O
access	O
or	O
create	O
audio	O
data	O
associated	O
with	O
an	O
HTML5	B-Application
audio	O
element	O
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
no	O
longer	O
relies	O
on	O
the	O
underlying	O
OS	O
for	O
text	O
layout/shaping	O
.	O
</s>
<s>
Instead	O
,	O
it	O
uses	O
HarfBuzz	B-Language
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
has	O
marked	O
a	O
major	O
change	O
in	O
performance	O
in	O
comparison	O
to	O
former	O
versions	O
3.6	O
and	O
3.5	O
.	O
</s>
<s>
The	O
browser	B-Application
has	O
made	O
significant	O
progress	O
in	O
Sunspider	O
JavaScript	B-Language
tests	O
as	O
well	O
as	O
improvements	O
in	O
supporting	O
HTML5	B-Application
.	O
</s>
<s>
Since	O
Firefox	B-Application
4.0	I-Application
Beta	O
5	O
,	O
hardware	B-General_Concept
acceleration	I-General_Concept
of	O
content	O
is	O
enabled	O
by	O
default	O
on	O
Windows	B-Application
Vista	I-Application
and	O
Windows	B-Device
7	I-Device
machines	O
using	O
Direct2D	B-Library
,	O
on	O
OS	B-Operating_System
X	I-Operating_System
using	O
Quartz	O
(	O
basically	O
CPU-only	O
)	O
,	O
and	O
Linux	B-Application
using	O
XRender	B-Device
.	O
</s>
<s>
Hardware	B-General_Concept
acceleration	I-General_Concept
of	O
compositing	O
is	O
enabled	O
by	O
default	O
on	O
Windows	B-Application
XP	I-Application
,	O
Windows	B-Application
Vista	I-Application
and	O
Windows	B-Device
7	I-Device
machines	O
using	O
Direct3D	B-Application
,	O
OS	B-Operating_System
X	I-Operating_System
and	O
Linux	B-Application
using	O
OpenGL	B-Application
.	O
</s>
<s>
Using	O
hardware	B-General_Concept
acceleration	I-General_Concept
allows	O
the	O
browser	B-Application
to	O
tap	O
into	O
the	O
computer	O
's	O
graphics	B-Architecture
processing	I-Architecture
unit	I-Architecture
,	O
lifting	O
the	O
burden	O
from	O
the	O
CPU	B-Device
and	O
speeding	O
up	O
the	O
display	O
of	O
web	O
pages	O
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
contains	O
support	O
for	O
the	O
"	B-Protocol
do	I-Protocol
not	I-Protocol
track	I-Protocol
"	I-Protocol
header	I-Protocol
,	O
an	O
emerging	O
standard	O
for	O
Web	O
privacy	O
.	O
</s>
<s>
The	O
header	O
signals	O
the	O
user	O
's	O
request	O
to	O
the	O
web	O
service	O
that	O
any	O
web	B-Application
visitor	I-Application
tracking	I-Application
service	O
be	O
disabled	O
.	O
</s>
<s>
It	O
also	O
introduced	O
the	O
ability	O
to	O
delete	O
flash	B-Operating_System
cookies	I-Operating_System
,	O
subjecting	O
them	O
to	O
the	O
same	O
deletion	O
rules	O
as	O
ordinary	O
HTTP	B-Application
cookies	I-Application
.	O
</s>
<s>
Release	O
Release	O
date	O
NotesAlpha	O
1	O
February	O
10	O
,	O
2010.Release	O
Notes	O
:	O
Mozilla	B-Operating_System
Developer	O
Preview	O
.	O
</s>
<s>
Mozilla.org	B-Operating_System
.	O
</s>
<s>
Firefox	O
3.7	O
(	O
Gecko	B-Language
1.9.3	O
)	O
Alpha	O
2	O
March	O
1	O
,	O
2010	O
Alpha	O
3	O
March	O
17	O
,	O
2010	O
Alpha	O
4	O
April	O
12	O
,	O
2010	O
Alpha	O
5	O
June	O
16	O
,	O
2010	O
Beta	O
1	O
July	O
6	O
,	O
2010	O
The	O
version	O
number	O
was	O
changed	O
to	O
4.0	O
(	O
Gecko	B-Language
's	O
2.0	O
)	O
Beta	O
2	O
July	O
27	O
,	O
2010	O
Beta	O
3	O
August	O
11	O
,	O
2010	O
Addition	O
of	O
"	O
switch	O
to	O
tab	O
"	O
,	O
which	O
allows	O
searching	O
for	O
opened	O
tabs	O
using	O
the	O
address	O
bar	O
for	O
quick	O
switching.Beta	O
4	O
August	O
24	O
,	O
2010	O
Beta	O
5	O
September	O
7	O
,	O
2010	O
Beta	O
6	O
September	O
14	O
,	O
2010	O
Beta	O
7	O
November	O
10	O
,	O
2010	O
Originally	O
scheduled	O
for	O
the	O
second	O
half	O
of	O
September	O
,	O
but	O
was	O
delayed	O
in	O
order	O
to	O
stabilize	O
the	O
new	O
JavaScript	B-Language
engine	I-Language
and	O
finish	O
the	O
planned	O
featuresBeta	O
8	O
December	O
22	O
,	O
2010	O
Beta	O
9	O
January	O
14	O
,	O
2011	O
Beta	O
10	O
January	O
25	O
,	O
2011	O
Beta	O
11	O
February	O
8	O
,	O
2011	O
Ship	O
eleventh	O
revision	O
of	O
beta	O
,	O
with	O
more	O
betaN+	O
hardblockers	O
fixed	O
(	O
14	O
betaN+	O
hardblockers	O
not	O
fixed	O
)	O
Beta	O
12	O
February	O
25	O
,	O
2011	O
Ship	O
twelfth	O
revision	O
of	O
beta	O
,	O
with	O
all	O
betaN+	O
hardblockers	O
fixed	O
.	O
</s>
<s>
Mozilla	B-Operating_System
senior	O
engineering	O
director	O
Damon	O
Sicore	O
,	O
urging	O
his	O
team	O
to	O
take	O
this	O
hill	O
and	O
push	O
through	O
to	O
ship	O
a	O
release	O
candidate	O
by	O
February	O
25.RC	O
1	O
March	O
9	O
,	O
2011	O
Complete	O
work	O
on	O
all	O
blocking	O
2.0:final	O
+	O
bugs	O
,	O
generate	O
release	O
candidatesRC	O
2	O
March	O
18	O
,	O
2011	O
Two	O
very	O
small	O
,	O
very	O
isolated	O
fixes	O
in	O
order	O
to	O
better	O
protect	O
Firefox	B-Application
4	I-Application
users.4.0	O
March	O
22	O
,	O
2011	O
Release	O
final	O
version	O
of	O
Firefox	O
4.0.4.0.1	O
April	O
28	O
,	O
2011	O
Fixed	O
several	O
security	O
and	O
stability	O
issues	O
.	O
</s>
<s>
On	O
22	O
March	O
2011	O
,	O
and	O
during	O
the	O
24-hour	O
launch	O
period	O
,	O
Firefox	B-Application
4	I-Application
received	O
7.1	O
million	O
downloads	O
,	O
as	O
counted	O
and	O
verified	O
by	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
.	O
</s>
<s>
Before	O
that	O
date	O
,	O
3	O
million	O
people	O
downloaded	O
the	O
second	O
release	O
candidate	O
of	O
the	O
browser	B-Application
,	O
which	O
later	O
became	O
the	O
final	O
version	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
the	O
new	O
version	O
of	O
the	O
browser	B-Application
received	O
10	O
million	O
downloads	O
on	O
the	O
first	O
day	O
.	O
</s>
<s>
Notwithstanding	O
,	O
it	O
fell	O
behind	O
the	O
previous	O
record	O
established	O
by	O
the	O
launch	O
of	O
Firefox	B-Language
3	I-Language
in	O
2008	O
,	O
which	O
was	O
8	O
million	O
.	O
</s>
<s>
Second-day	O
downloads	O
for	O
the	O
browser	B-Application
were	O
reported	O
to	O
be	O
8.75	O
million	O
,	O
but	O
the	O
lack	O
of	O
an	O
official	O
representative	O
from	O
Guinness	O
to	O
monitor	O
the	O
numbers	O
,	O
made	O
the	O
record	O
attained	O
by	O
Firefox	B-Language
3	I-Language
only	O
unofficially	O
been	O
broken	O
.	O
</s>
<s>
On	O
the	O
official	O
launch	O
date	O
,	O
the	O
usage	O
share	O
for	O
the	O
Firefox	B-Application
4	I-Application
was	O
1.95	O
%	O
,	O
which	O
was	O
0.34	O
%	O
higher	O
than	O
the	O
previous	O
day	O
according	O
to	O
analytics	O
website	O
StatCounter	O
.	O
</s>
<s>
As	O
a	O
comparison	O
,	O
the	O
usage	O
share	O
for	O
the	O
Internet	B-Application
Explorer	I-Application
9	I-Application
on	O
March	O
22	O
was	O
0.87	O
%	O
,	O
and	O
it	O
was	O
released	O
the	O
prior	O
week	O
,	O
on	O
March	O
14	O
.	O
</s>
<s>
A	O
potential	O
factor	O
on	O
Firefox	B-Application
4	I-Application
's	O
higher	O
usage	O
share	O
is	O
that	O
the	O
latter	O
supports	O
both	O
Windows	B-Application
2000	I-Application
and	O
XP	B-Application
,	O
two	O
operating	O
systems	O
Internet	B-Application
Explorer	I-Application
9	I-Application
does	O
not	O
support	O
.	O
</s>
<s>
Also	O
,	O
at	O
launch	O
,	O
Mozilla	B-Operating_System
prompted	O
existing	O
customers	O
to	O
upgrade	O
their	O
browsers	B-Application
to	O
the	O
newer	O
version	O
,	O
something	O
Microsoft	O
had	O
n't	O
applied	O
to	O
users	O
of	O
older	O
versions	O
of	O
Internet	O
Explorer	O
.	O
</s>
<s>
Instead	O
,	O
Microsoft	O
prompted	O
users	O
to	O
upgrade	O
via	O
Windows	B-Application
Update	O
several	O
weeks	O
after	O
launch	O
.	O
</s>
<s>
On	O
March	O
26	O
,	O
2011	O
,	O
Firefox	B-Application
4	I-Application
's	O
usage	O
share	O
exceeded	O
that	O
of	O
the	O
10-year-old	O
and	O
discontinued	O
Internet	B-Application
Explorer	I-Application
6	I-Application
for	O
the	O
first	O
time	O
.	O
</s>
<s>
Also	O
on	O
that	O
date	O
,	O
the	O
browser	B-Application
's	O
usage	O
share	O
was	O
higher	O
than	O
all	O
versions	O
of	O
Safari	B-Application
,	O
Opera	B-Application
and	O
older	O
versions	O
of	O
Firefox	B-Application
with	O
the	O
exception	O
of	O
Firefox	B-Protocol
3.6	I-Protocol
.	O
</s>
<s>
As	O
a	O
reference	O
,	O
Internet	B-Application
Explorer	I-Application
9	I-Application
's	O
usage	O
share	O
first	O
exceeded	O
that	O
of	O
Internet	B-Application
Explorer	I-Application
6	I-Application
on	O
May	O
1	O
,	O
2011	O
(	O
48	O
days	O
after	O
release	O
)	O
,	O
and	O
Internet	B-Application
Explorer	I-Application
9	I-Application
became	O
the	O
second	O
most	O
used	O
version	O
of	O
Internet	O
Explorer	O
for	O
the	O
first	O
time	O
on	O
May	O
22	O
,	O
2011	O
(	O
69	O
days	O
after	O
release	O
)	O
.	O
</s>
<s>
According	O
to	O
StatCounter	O
,	O
Firefox	B-Application
4	I-Application
reached	O
its	O
usage	O
share	O
peak	O
of	O
16.7	O
%	O
on	O
June	O
19	O
,	O
2011	O
.	O
</s>
<s>
After	O
that	O
date	O
,	O
it	O
started	O
to	O
decline	O
due	O
to	O
weekly	O
trends	O
and	O
the	O
release	O
of	O
Firefox	B-Application
5	O
.	O
</s>
<s>
Firefox	B-Application
4	I-Application
represents	O
a	O
departure	O
in	O
user	B-Application
interface	I-Application
layout	O
and	O
behaviour	O
from	O
previous	O
versions	O
.	O
</s>
<s>
The	O
Firefox	B-Application
button	O
groups	O
the	O
menus	O
in	O
Firefox	B-Application
4	I-Application
.	O
</s>
<s>
It	O
is	O
displayed	O
by	O
default	O
on	O
the	O
Windows	B-Device
7	I-Device
and	O
Windows	B-Application
Vista	I-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
The	O
Menu	O
bar	O
can	O
be	O
restored	O
by	O
selecting	O
"	O
Options	O
"	O
from	O
the	O
Firefox	B-Application
button	O
menu	O
and	O
checking	O
"	O
Menu	O
Bar	O
"	O
.	O
</s>
<s>
Certain	O
menu	O
items	O
,	O
such	O
as	O
"	O
Page	O
Info	O
"	O
and	O
"	O
Import	O
"	O
(	O
for	O
importing	O
bookmarks	O
and	O
other	O
browser	B-Application
data	O
)	O
,	O
are	O
not	O
available	O
from	O
the	O
Firefox	B-Application
button	O
menu	O
but	O
remain	O
available	O
from	O
the	O
Menu	O
bar	O
.	O
</s>
<s>
A	O
prompt	O
to	O
save	O
the	O
session	O
(	O
tabs	O
and	O
windows	B-Application
)	O
was	O
presented	O
by	O
default	O
in	O
Firefox	B-Language
3	I-Language
,	O
with	O
the	O
session	O
restored	O
on	O
the	O
next	O
start	O
if	O
the	O
user	O
selected	O
the	O
"	O
Save	O
&	O
Quit	O
"	O
option	O
.	O
</s>
<s>
In	O
Firefox	B-Application
4	I-Application
,	O
all	O
sessions	O
are	O
saved	O
.	O
</s>
