DOM, Layers, All

Well i try to use all in my codes to get more support, for example:

if ([COLOR=”Green”]document.getElementById[/COLOR]){
[COLOR=”Red”]String[/COLOR]
}
else{
if ([COLOR=”Green”]document.layers[/COLOR]){
[COLOR=”Red”]String[/COLOR]
}
else{
if ([COLOR=”Green”]document.all[/COLOR])
[COLOR=”Red”]String[/COLOR]
}
else{

[COLOR=”Red”]String[/COLOR]
}
}
}
}

But i was wondering, is there a better way to do this? And also lets say a function is as follows:

function Example(id)

and for document layers for example is it best to do:

document.layers.id.
id.
document.layers[id].

I normally only do one of them for all my scripts however every code seams to do it differently. Does it not matter? Also can someone point me to somewhere i can find out more about this, google is too vague.

what is the correct way to string: document.all and document.layers, im fine with DOM. also is there any more methods i need to take into account?

Thanks a lot.

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