The answer to 'hardwood floor stained' is that there are several common causes, including spills, pet accidents, heavy foot traffic, and improper cleaning. Symptoms may include discoloration, fading, or a dull appearance. Solutions can range from DIY cleaning and refinishing to hiring a professional floor refinishing service, depending on the severity of the stain.
For minor stains, you may be able to DIY by using a hardwood floor cleaner or a mixture of warm water and mild soap. For deeper, set-in stains or extensive damage, it's best to call in a professional hardwood floor refinishing company. They have the tools and expertise to sand down the floors, apply new stain and sealant, and restore the floors to like-new condition.