procedure TForm1.Button1Click(Sender: TObject);
begin
Webbrowser1.Navigate('D:\a.html');
  //启动一个网站的网页
end;

procedure TForm1.Button2Click(Sender: TObject);
var     
  Range:IHTMLTxtRange;
begin
  Range := ((WebBrowser1.Document as IHTMLDocument2).body as
    IHTMLBodyElement).createTextRange;
  Range.collapse(False);
  Range.pasteHTML(' <br> <b>大家好,我是老李,csdn Id Laoli </b>');
//加入你要加的东西
end;

C/C++ code

/*
  // WebBrowser->Navigate(L"D:\a.html");

   sorry,这句路径在C++中应该是 WebBrowser->Navigate(L"D:\\a.html") ;
*/

void __fastcall TForm1::Button1Click(TObject *Sender)
{
Webbrowser1->Navigate('D:\\a.html');
}
楼上正解

非常感谢！