Some one told me that if you use "regular" water to make dough it makes some air bubbles inside the dough. But if you leave the water to stand in a jar for 24 hours it will somehow change its properties and would not affect the dough in any way. Sounds weird to me.

It's quite simple. Water from the faucet picks up air as it flows down into your container; agitation is a good way to dissolve anything in water. Your tap water may also be supersaturated in dissolved gases, if you get it from a well.

But if you let the water stand overnight, most of the dissolved gas will leave. That's because standing water can't hold much gas.

Assuming that what you've been told is true (which I doubt, I'm a baker myself), extra bubbles in dough might stem from the trapping of dissolved gas released from the water. My guess is that they come from the yeast or whatever other leavening agent you're using; as I said, water doesn't hold that much gas.

Dan Berger