plugins | NN 3 IE 4 DOM n/a
Navigator and Internet Explorer both have a plugins array, but they are quite different collections of objects. Navigator's plugins array is a property of the navigator object. Each item in the navigator.plugins array represents a plugin that is installed in the browser (actually just registered with the browser when the browser last loaded). See the plugin object. Internet Explorer's plugins collection belongs to the document object and essentially mirrors the embeds collection: a collection of all EMBED elements in the document. An EMBED element may well, indeed, launch a plugin, but not necessarily. Nor does Internet Explorer provide JavaScript access to the installed plugins in the same way that Navigator does.
Object Model Reference
NN | navigator.plugins
IE | document.plugins

length | NN 3 IE 4 DOM n/a
| Read-only
Returns the number of elements in the collection.
Example
    var IEhowMany = document.embeds.length
    var NNhowMany = navigator.embeds.length
Value Integer.

item( ) | NN n/a IE 4 DOM n/a
item(index[, subindex]) Returns a single object or collection of objects corresponding to the element matching the index value (or, optionally, the index and subindex values).
Returned Value One object or collection (array) of objects. If there are no matches to the parameters, the returned value is null.
Parameters
index | When the parameter is a zero-based integer, the returned value is a single element corresponding to the said numbered item in source code order (nested within the current element); when the parameter is a string, the returned value is a collection of elements whose id or name properties match that string.
subindex | If you specify a string value for the first parameter, you may use the second parameter to specify a zero-based integer to retrieve a specific element from the collection whose id or name properties match the first parameter's string value.