Here's a list of the percentage of JavaScript features that work in each of the popular browsers. Sadly, it looks like only about 31% of the features work with both 3.0 and above browsers. I know site developers who have decided to simply not use JavaScript at all rather than mess with the compatibility issues.
August 26, 1998
IE 3 & 4
243
31.68%
Nav 3 & 4
373
48.63%
IE4 & NAV 4
425
55.41%
All 4 browsers
240
31.29%
A further caveat: This suggests areas that you should check rather than just go on my say so. Some features could get implemented at intermediate releases such as 4.04 where they weren't available at 4.03 or might be available only on certain platforms. So we are simplifying things a little when we talk about Nav 3 vs. Nav 4.
There is a Web Standards pressure group that is trying to get some groundswell of public opinion going to make Microsoft and Netscape toe the line and at least support the W3C and other published standards. They are at http://www.webstandards.org/ and are called 'The Web Standards Project'.
Here's the whole, frightening list layer through screen:
layer
above
No
No
No
Yes
layer
background
No
No
No
Yes
layer
below
No
No
No
Yes
layer
bgColor
No
No
No
Yes
layer
captureEvents()
No
No
No
Yes
layer
clip
No
No
No
Yes
layer
document
No
No
No
Yes
layer
handleEvents()
No
No
No
Yes
layer
hidden
No
No
No
Deprecated
Deprecated - Use layer.visibility instead
layer
layers[]
No
No
No
Deprecated
Deprecated - use layoer.document.layers instead
layer
left
No
No
No
Yes
layer
lowd()
No
No
No
Yes
layer
moveAbove()
No
No
No
Yes
layer
moveBelow()
No
No
No
Yes
layer
moveBy()
No
No
No
Yes
layer
moveTo()
No
No
No
Yes
layer
moveToAbsolute()
No
No
No
Yes
layer
name
No
No
No
Yes
layer
offset()
No
No
No
Deprecated
Deprecated use layer.moveBy() instead
layer
pageX
No
No
No
Yes
layer
pageY
No
No
No
Yes
layer
parentLayer
No
No
No
Yes
layer
releaseEvents()
No
No
No
Yes
layer
resizeBy()
No
No
No
Yes
layer
resizeTo()
No
No
No
Yes
layer
routeEvent()
No
No
No
Yes
layer
siblingAbove
No
No
No
Yes
layer
siblingBelow
No
No
No
Yes
layer
src
No
No
No
Yes
layer
top
No
No
No
Yes
layer
visibility
No
No
No
Yes
layer
window
No
No
No
Yes
layer
x
No
No
No
Yes
layer
y
No
No
No
Yes
layer
zIndex
No
No
No
Yes
link
hash
Yes
Yes
Yes
Yes
link
host
Yes
Yes
Yes
Yes
link
hostname
Yes
Yes
Yes
Yes
link
href
Yes
Yes
Yes
Yes
link
onclick
Bugged on Windows
Yes
Yes
Yes
Enhanced in JS 1.1, Bugged in IE 3 on Windows
link
onmouseout
No
Yes
Yes
Yes
link
onmouseover
Yes
Yes
Yes
Yes
link
pathname
Yes
Yes
Yes
Yes
link
port
Yes
Yes
Yes
Yes
link
protocol
Yes
Yes
Yes
Yes
link
search
Yes
Yes
Yes
Yes
link
target
Yes
Yes
Yes
Yes
link
text
No
No
No
Yes
link
x
No
No
No
Yes
link
y
No
No
No
Yes
location
hash
Yes
Yes
Yes
Yes
location
host
Yes
Yes
Yes
Yes
location
hostname
Yes
Yes
Yes
Yes
location
href
Yes
Yes
Yes
Yes
location
pathname
Yes
Yes
Yes
Yes
location
port
Yes
Yes
Yes
Yes
location
protocol
Yes
Yes
Yes
Yes
location
reload()
No
Yes
Yes
Yes
location
replace()
No
Yes
Yes
Yes
location
search
Yes
Yes
Yes
Yes
math
abs()acos()
Yes
Yes
Yes
Yes
math
asin()
Yes
Yes
Yes
Yes
math
atan()
Yes
Yes
Yes
Yes
math
atan2()
Yes
Yes
Yes
Yes
math
ceil()
Yes
Yes
Yes
Yes
math
cos()
Yes
Yes
Yes
Yes
math
E
Yes
Yes
Yes
Yes
math
exp()
Yes
Yes
Yes
Yes
math
floor()
Yes
Yes
Yes
Yes
math
LN10
Yes
Yes
Yes
Yes
math
LN2
Yes
Yes
Yes
Yes
math
log()
Yes
Yes
Yes
Yes
math
LOG10E
Yes
Yes
Yes
Yes
math
LOG2E
Yes
Yes
Yes
Yes
math
max()
Yes
Yes
Yes
Yes
math
min()
Yes
Yes
Yes
Yes
math
PI
Yes
Yes
Yes
Yes
math
pow()
Yes
Yes
Yes
Yes
math
random()
No
Yes
Yes
Yes
math
round()
Yes
Yes
Yes
Yes
math
sin()
Yes
Yes
Yes
Yes
math
sqrt()
Yes
Yes
Yes
Yes
math
SQRT1_2
Yes
Yes
Yes
Yes
math
SQRT2
Yes
Yes
Yes
Yes
math
tan()
Yes
Yes
Yes
Yes
mimeTypes
description
No
No
Yes
Yes
mimeTypes
enabledPlugin
No
No
Yes
Yes
mimeTypes
suffixes
No
No
Yes
Yes
mimeTypes
type
No
No
Yes
Yes
navigator
appCodeName
Yes
Yes
Yes
Yes
navigator
appName
Yes
Yes
Yes
Yes
navigator
appVersion
Yes
Yes
Yes
Yes
navigator
javaEnabled()
No
Yes
Yes
Yes
navigator
language
No
No
No
Yes
navigator
mimeTypes[]
No
Bugged
Yes
Yes
Bugged in IE 4
navigator
platform
No
Yes
No
Yes
navigator
plugins.refresh()
No
No
Yes
Yes
navigator
plugins[]
No
Bugged
Yes
Yes
Bugged in IE 4
navigator
preference()
No
No
No
Yes
Requires priv settings on Nav 4
navigator
savePreferences()
No
No
No
Yes
Requires priv settings on Nav 4
navigator
systemLanguage
No
No
No
Yes
navigator
taintEnabled()
No
Deprecated
Deprecated
Deprecated
Deprecated - Do not use
navigator
userAgent
Yes
Yes
Yes
Yes
navigator
userLanguage
No
No
No
Yes
netscape
No
No
Yes
Yes
number
MAX_VALUE
No
Yes
Yes
Yes
number
MIN_VALUE
No
Yes
Yes
Yes
number
NaN
No
Yes
Yes
Yes
number
NEGATIVE_INFINITY
No
Yes
Yes
Yes
number
POSITIVE_INFINITY
No
Yes
Yes
Yes
number
toString()
No
Yes
Yes
Yes
object
assign()
No
No
Deprecated
Deprecated
Deprecated in favour of object.watch
object
constructor
No
Yes
Yes
Yes
object
eval()
No
No
Deprecated
Deprecated
Deprecated in Nav 4
object
toString()
Yes
Yes
Yes
Yes
object
unwatch()
No
No
No
Yes
object
valueOf()
No
Yes
Yes
Yes
object
watch()
No
No
No
Yes
option
defaultSelected
Yes
Yes
Yes
Yes
option
index
Yes
Yes
Yes
Yes
option
selected
Yes
Yes
Yes
Yes
option
text
Limited
Yes
Yes
Yes
Became writable in JS 1.1
option
value
Yes
Yes
Yes
Yes
packages
java
No
No
Yes
Yes
packages
netscape
No
No
Yes
Yes
packages
sun
No
No
Yes
Yes
password
blur()
Yes
Yes
Yes
Yes
password
defaultValue
Yes
Yes
Yes
Yes
password
focus()
Yes
Yes
Yes
Yes
password
form
Yes
Yes
Yes
Yes
password
name
Yes
Yes
Yes
Yes
password
onblur
Yes
Yes
Yes
Yes
password
onchange
Yes
Yes
Yes
Yes
password
onfocus
Yes
Yes
Yes
Yes
password
select()
Yes
Yes
Yes
Yes
password
type
No
Yes
Yes
Yes
password
value
Bugged
Yes
Limited
Yes
Modified in JS 1.2. Possibly buggy in IE 3
plugin
description
No
No
Yes
Yes
plugin
filename
No
No
Yes
Yes
plugin
length
No
No
Yes
Yes
plugin
name
No
No
Yes
Yes
PriviledgeManager
disablePriviledge()
No
No
No
Yes
PriviledgeManager
enablePriviledge()
No
No
No
Yes
radio
blur()
Yes
Yes
Yes
Yes
radio
checked
Yes
Yes
Yes
Yes
radio
click()
Yes
Yes
Yes
Yes
radio
defaultChecked
Yes
Yes
Yes
Yes
radio
focus()
Yes
Yes
Yes
Yes
radio
form
Yes
Yes
Yes
Yes
radio
name
Yes
Yes
Yes
Yes
radio
onblur
Yes
Yes
Yes
Yes
radio
onclick
Limited
Yes
Yes
Yes
Enhanced in JS 1.1
radio
onfocus
Yes
Yes
Yes
Yes
radio
type
No
Yes
Yes
Yes
radio
value
Bugged
Yes
Yes
Yes
Possibly buggy in IE 3
RegExp
$n
No
Yes
No
Yes
RegExp
$_
No
Deprecated
No
Deprecated
Deprecated - do not use
RegExp
compile()
No
Yes
No
Yes
RegExp
exec()
No
Bugged
No
Yes
Buggy in IE 4
RegExp
global
No
No
No
Yes
RegExp
ignoreCase
No
No
No
Yes
RegExp
input
No
Bugged
No
Yes
Broken in IE 4
RegExp
lastIndex
No
No
No
Yes
RegExp
lastMatch
No
No
No
Yes
RegExp
lastParen
No
No
No
Yes
RegExp
leftContext
No
No
No
Yes
RegExp
multiline
No
No
No
Yes
RegExp
rightContext
No
No
No
Yes
RegExp
source
No
Yes
No
Yes
RegExp
test()
No
Bugged
No
Yes
Bugged in IE 4
RegExp
["$'"]
No
Deprecated
No
Deprecated
Deprecated - do not use
RegExp
["$*"]
No
Deprecated
No
Deprecated
Deprecated - do not use
RegExp
["$+"]
No
Deprecated
No
Deprecated
Deprecated - do not use
RegExp
["$`"]
No
Deprecated
No
Deprecated
Deprecated - do not use
RegExp
["$|&"]
No
Deprecated
No
Deprecated
Deprecated - do not use
reset
blur()
Yes
Yes
Yes
Yes
reset
click()
Yes
Yes
Yes
Yes
reset
focus()
Yes
Yes
Yes
Yes
reset
form
Yes
Yes
Yes
Yes
reset
name
Yes
Yes
Yes
Yes
reset
onblur
Yes
Yes
Yes
Yes
reset
onclick
Limited
Yes
Yes
Yes
Enhanced in JS 1.1
reset
onfocus
Yes
Yes
Yes
Yes
reset
type
No
Yes
Yes
Yes
reset
value
Bugged
Yes
Yes
Yes
Possibly buggy in IE 3
This is a prety long list so we have split it up over several pages. They are still a bit slow to load due to their size.
