code: public void setAlt(String alt)
      {
          _state.registerAttribute(AbstractHtmlState.ATTR_GENERAL, ALT, alt, true);
      }
docs: Sets the property to specify the alt text of the image.
  @param alt the image alignment.
  @jsptagref.attributedescription Specifies alternate text for the area.
  @jsptagref.databindable false
  @jsptagref.attributesyntaxvalue <i>string_alt</i>
  @netui:attribute required="false" rtexprvalue="true"
  description="Specifies alternate text for the area."