Becoming pregant..

I recently read on a website that there was just a 24 hour window in which you can become pregnant, Is this true? How do you go about working out when this window is for an individual?

(I ask as we want to avoid this window)

That's what I have always heard too. There are only 24 hours out of a whole month that a woman can get pregnant. I worked it out somehow when I was trying for my second child but I can't remember exactly what I did. It worked though.
Try this link http://www.4woman.gov/Pregnancy/ovulation1.cfm It's supposed to help you figure out when you are ovulating so you can get pregnant, you can use it the opposite way LOL