IE Com Object, Difference between methods .Navigate and .Navigate2
The difference is in the first argument URL. Here is what MSDN says:
URL: A String expression that evaluates to the URL, full path, or Universal Naming Convention (UNC) location and name of the resource to display.
URL: A variable or expression that evaluates to the URL of the resource to display, the full path to the file location, or a PIDL that represents a folder in the Shell namespace.
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This method extends the Navigate method to allow for Shell integration; however, this method does not make Navigate obsolete. The original method can still be used for URL navigations.