shannasays,
It is crucial to have the exact paixel x pixel size.
Did you use Save for Web so you could see that the image size was right in the Image Size window?
Or did you Export, and in that case did you set the resolution to 72? If you set it to 300 or whatever else than 72, you wil get pixelation/blurriness because of resampling.
It is important to have Art Optimized ticked. in Save for Web it is hidden away in the Image Size window.