Dialog windows are a special kind of window supported by MSIE, principally to provide a more sophisticated alternative to an alert(), confirm() or prompt() dialog.

This property yields the width of such a dialog window which can be changed by assigning a value to this property from a script running in the window.

The value returned will be a value and a measurement unit in the same style as would be used with a CSS positioning style property. This means it will be a string and not a numeric value and will need to be parsed carefully.