// uses WinInet, idHTTP;

function UrlExists(sUrl: String; bAllowRedirects: Boolean = false): Boolean;
begin
  with TidHTTP.Create(nil) do
  try
    HandleRedirects := bAllowRedirects;
    Head(sUrl);
    Result := Response.ResponseCode = HTTP_STATUS_OK;
  finally
    Free;
  end;
end;