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Syntax: choose from drop down list
For Refresh-type walks, this controls how the Expires header is
used. Set to No the Expires header will be ignored. Set to
Limited the Expires header will be used, but limited by the
Minimum Refresh Time and Maximum Refresh Time.
Set to Yes the Expires header will be treated as definitive.
Invalid and out of range headers will be ignored, with the exception of "0".