Code:

{ Alternative Text for a image of a TWebBrowser }

procedure TForm1.Button1Click(Sender: TObject);

var

HTMLDocument2Ifc: IHTMLDocument2;

HTMLSelectionObjectIfc: IHTMLSelectionObject;

HTMLTxtRangeIfc: IHTMLTxtRange;

begin

HTMLDocument2Ifc := WebBrowser1.Document as IHTMLDocument2;

HTMLDocument2Ifc.execCommand('InsertImage', False, '');

HTMLSelectionObjectIfc := HTMLDocument2Ifc.selection;

if HTMLSelectionObjectIfc.type_ = 'Control' then HTMLSelectionObjectIfc.Clear;

HTMLTxtRangeIfc := HTMLSelectionObjectIfc.createRange as IHTMLTxtRange;

HTMLTxtRangeIfc.pasteHTML('<image alt="Hello" src="c:\test.gif"> ');

end;