Spots all over the inside side of my windows?

Question

I noticed while I was cleaning my windows that there are all sorts of little spots, white, brown, and gray, that are all over my windows unless the window is blocked by something like a bookcase. They're obviously no water spots and they're even in the living room so it can't be food. My mom was thinking that they're from bugs hitting the windows or pooping on the windows. Anyone know?

Answer 1

Your mom is a smart woman.

Answer 2

Yes, more than likely, your mom is right.

Answer 3

Yes it is fly and bug poo.  Washes off with soapy water.  Nasty little creatures eh?  We have a conservatory which seems to attract flies/bugs etc. and they do this over everything!