The answer to 'why is my window stained' is that there are a few common causes, including mineral deposits from hard water, environmental pollution, or improper cleaning methods. Mineral stains appear as white, cloudy spots or streaks, while environmental stains can look like dark, hazy marks.
The best solution depends on the type of stain. For mineral deposits, you can try cleaning with a vinegar or lemon juice solution. For environmental stains, use a commercial window cleaner or make your own solution with warm water and dish soap. If the stains are stubborn or you're unsure of the cause, it's best to call a professional window cleaning service to properly diagnose and treat the issue.