procedure TForm1.Button1Click(Sender: TObject);

            var

            Doc:IHTMLDocument2;

            form:ithmlformelement;
userinputelement,pwdinputelement:ihtmlinputelement;

begin
doc:=webbrowser1.document as ihtmldocument2;
userinputelement:=(doc.all.item('user'(也就是网页中用户名控件的名字),0) as ihtmlinputelement);
userinputelement.value:=edit1.text;(也就是你要向网页输入的东西)
pwdinputelement:=(doc.all.item('password',0) as ihtmlinputelement);
pwdinputelement:=edit2.text;
form:=(doc.all.item('login_form',0) as ihtmlformelement):
form.submit;
end; 

procedure TForm1.Button1Click(Sender: TObject);

var

                doc2:IHTMLDocument2;

                o : Olevariant;

                ole_index: OleVariant;

                frame_dispatch: IDispatch;

                frame_win: IHTMLWindow2;

                frame_doc: IHTMLDocument2;      

begin

              begin

                  doc2 := WebBrowser1.Document as IHTMLDocument2;

                  ole_index:=0;

                  frame_dispatch := doc2.Frames.Item(ole_index);

                  if frame_dispatch <> nil then

                  begin

                      frame_win := frame_dispatch as IHTMLWindow2;

                      frame_doc := frame_win.document;

                     // memo1.lines.add(IHTMLDocument2(frame_doc).body.outerHTML);

                  End;

            end;