function isconnected : Boolean ; 
var
 connectiontype: DWORD ;
begin
 connectiontype:=INTERNET_CONNECTION_MODEM // тип соединения
 +INTERNET_CONNECTION_LAN
 +INTERNET_CONNECTION_PROXY ;
 Result:=InternetGetConnectedState(@connectiontype,0);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
 if isconnected=true then showmessage('Connected') 
 else showmessage('No Connection');
end;