The code attempted to decode an improperly formed Uniform Resource Identifier (URI). URIs have a special syntax; most non-alphanumeric characters must be encoded before they can be used in a URI. The encodeURI and encodeURIComponent methods cannot create a URI from a normal JScript string.
A complete URI is comprised of a sequence of components and separators. The general form is:
The names in angle brackets represent components, and the ":", "/", ";" and "?" are reserved characters used as separators.
To correct this error
Ensure that the code is trying to decode valid URIs only. For example, a normal JScript string may not be a valid URI because it may contain invalid characters.