1 Samuel 5:4

But when they got up early the next morning, behold, Dagon had (again) fallen on his face on the ground before the ark of the Lord, and his head and both palms of his hands were (lying) cut off on the threshold; only the trunk (portion) of (the idol of) Dagon was left on him. 

The Philistines made the mistake of placing a false god next to the true God. People realize that there is something about the true God that they want, but they still want to keep their idols. For example, the two cannot exist together: God and my career, God and money, God and entertainment. God will not share His throne with idols.