Returns or sets the descriptive (alternative) text string for a Shape or ShapeRange object when the object is saved to a Web page. Read/write String.
Remarks
The alternative text can be displayed either in place of the shape’s image in the Web browser , or directly over the image when the mouse pointer hovers over the image (in browsers that support these features).
Example
This example sets the alternative text for the first shape on the first worksheet to a description of the shape.
Worksheets(1).Shapes(1).AlternativeText = "Concentric circles"