Specifies extra advisory information about the weblet. This is usually extra non-essential information to help a user understand the purpose of the weblet. Different browsers may handle it in different ways. For example, most desktop browsers will display it as a tooltip when the mouse hovers over the weblet. Assistive technologies like screen readers will read it to the user. At the time of this writing, mobile device browsers will ignore it.
Default value
Blank
Valid values
Any valid HTML attribute string.
