formtarget [HTML5]

If the input element is a submit button or image, this attribute is a name or keyword indicating where to display the response that is received after submitting the form. This is a name of, or keyword for, a browsing context (for example, tab, window, or inline frame). If this attribute is specified, it overrides the target attribute of the elements's form owner. The following keywords have special meanings:
  _self: Load the response into the same browsing context as the current one. This value is the default if the attribute is not specified.
  _blank: Load the response into a new unnamed browsing context.
  _parent: Load the response into the parent browsing context of the current one. If there is no parent, this option behaves the same way as _self.
  _top: Load the response into the top-level browsing context (that is, the browsing context that is an ancestor of the current one, and has no parent). If there is no parent, this option behaves the same way as _self.