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_formActionTarget is optional and only taken into account when _formActionUrl is specified. It can be set to one of the values: frame, parent, top (lower case). It defaults to Frame frame if not specified.
When the _formActionUrl parameter is set but no Url is given (i.e. ...&_formActionUrl =&embed=...) the top frame will be closed. It is as if you set Form Action to Close" in the Form Designer.
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