1. Crisp Edges

Gecko's default behavior when zooming is to interpolate pixels. This has a blurring effect on images. It can be turned off by using the image-rendering css property with the value -moz-crisp-edges. Here is how to set this globally:

register_user_stylesheet(make_css_data_uri(
    ["* { image-rendering: -moz-crisp-edges; }"]));

• More information on the image-rendering property: https://developer.mozilla.org/En/CSS/Image-rendering