.......
> permanently connected between the socket and the header. THe rest of the
> lines (Vdd,Vss,MCLR,and two others which I cannot remember at this point,
> just look at www.microchip.com at the programming specifications, the
> first page of the sheet lists them). These lines are switched between the
> header and the IDC connector (going to the programmer). You can determine
> the pinout of the programmer's IDC header by using an ohmmeter to check
> conductivity to each of the 5 pins involved in the programming. If you
> want, I can take a look at the one I built and tell you the pinout, but I
> am at work right now and it would probably be quicker for you to just
> check it with the meter.
>
> I built mine in a day, it cost about $10, and it works great!

Is switching Vss necessary?