const
OLECMDID_OPTICAL_ZOOM = 63;
procedure TForm1.FormShow(Sender: TObject);
var
pvaIn: OleVariant;
begin
WebBrowser1.Navigate('about:');
while WebBrowser1.QueryStatusWB(OLECMDID_PRINT) <> OLECMDF_SUPPORTED or OLECMDF_ENABLED do
Application.ProcessMessages;
pvaIn := 100;
WebBrowser1.ExecWB(OLECMDID_OPTICAL_ZOOM, OLECMDEXECOPT_DODEFAULT, pvaIn);
end;