procedure
TForm1.WebBrowser1ProgressChange(ASender: TObject;
Progress,
  ProgressMax: Integer);
begin
  ProgressBar1.Max:=ProgressMax;
  if Progress = -1 then
     //ProgressBar1.Visible:=false
  else
  begin
    ProgressBar1.Position
:=
Progress;
    ProgressBar1.Visible := True;
  end;
  if  ProgressBar1.Position = ProgressMax then
    //ProgressBar1.Visible:=False;
end;