If you have added a Gallery or Thumbnail List to your page and images are seem to be blurry it usually means that preview images or thumbnails are smaller by size than the Gallery itself.
In order to make your Gallery look better please set appropriate size for preview and thumbnail images.
Please choose optimal sizes while adding the new items in order to avoid the blurry images in your Gallery.
It does not mean that you should use the dimensions from screenshot above but try to adjust them to fit your exact Gallery. And then your gallery will look much better.