Maybe you have heard the phrase "the writing on the wall." Like, someone will say "I can see the writing on the wall." And this means a bad thing is about to happen, so you had better run and hide or at least flatten yourself against the ground so that you are mostly invisible.
One time when Mom was a little girl, she wrote on the wall in her house. But she was so young that she did not know how to write yet, so she just drew pictures with a crayon. Mom got into a lot of trouble for doing this. Her mom made her wash all the drawings off the wall, which just goes to show that not everybody takes the writing on the wall as a serious warning or even as beautiful artwork to be preserved forever.
Dogs don't really spend much time reading writing on the wall because this writing is often above our eye level. Instead, we like to read the writing on the sidewalk. We read this writing because it is easy to see when we are sniffing around, looking for yummy food fragments to eat. Writing on the sidewalk is usually not a warning, like writing on the wall is. Sidewalks are almost always made of concrete, and wet concrete has the quality of making people want to mark it somehow, like by writing on it or putting a handprint on it. This is similar to when a dog marks a tree by peeing on it, except a mark on concrete lasts lots longer.
Anyway, all of this just goes to prove that if you keep your eyes open while you are walking around the neighborhood, you might see some interesting writing on the sidewalks. And also if you keep your eyes open, you are less likely to trip and fall down!