What is broken window theory?

The Broken Window Theory is this: If one single window is broken on a building, it inevitably leads to more broken windows on that same structure. Windows are too tantalizingly fun to break that neighborhood-lums can hardly resist the allure of what appears to be a run-down, uncared-for building. The theory extends beyond housing and into practically any area, including litter and graffiti. The presence of these undesirable traits rapidly accelerates the damage caused. 

If the situation continues to deteriorate, the building eventually becomes uninhabitable, perhaps to the point of not being worth restoration. To prevent this from happening, you should fix the window within one week of breakage. If the issue is litter, clean the sidewalk every day. By up-keeping the area, active citizens remain in the neighborhood, which also greatly reduces the chance of ongoing disturbance.