The voltage divider between the weak pullup and the pulldown resistor is clear. In my previous posts I clarified that the resistance value of the pulldown has to be low enough to ensure the input is below VIL.
Ok, This is - I hope - not war but an argument between friends.
I come out in support of pullups because they match the '51 technology better than pulldowns.
Michael, I think we are both missing the point: Shazad is talking about detectins a float, that is impossible. What is possible is to convert the float into a high or a low. So, if the non-floating state is a high, use pulldowns, if the non-floating state is a low (preferred) use pullups, if the nonfloating state is either you are screwed

If your "float" is a relay or sensor contact contact one side to ground and the other side to your input. If you are in a noiusy environment or using P0 you will need pullups.

I hope i can join the bear party but i'm a muslim.... Michael do you have any thing else to offer me.
The Quoran does not say "do not drink" it says "do not get drunk" so you can join us for the first two.

Erik