You'd have to tell us more about the file you're working on. Is the blurry area in an imported graphic? Is it something that's been created in InDesign (no way to tell that in your attachment). You should check View > Display Performance and make sure it's set as High Quality. If it's a placed image, what is the resolution of the image. Other things that would help us: Please tell us what operating system (exactly) you're running. Please tell us (exactly) what InDesign version you're using.