Unfortunately this must be set by site, but on retina screens on MacOS, many browsers blur small images, such as 88×31 buttons.
You can overcome this, at least for the images on your site, by adding this CSS to your site:
img, div {
image-rendering: optimizeSpeed;
image-rendering: -moz-crisp-edges;
image-rendering: -webkit-optimize-contrast;
image-rendering: optimize-contrast;
image-rendering: pixelated;
-ms-interpolation-mode: nearest-neighbor;
}
You should add any element that might have a CSS background image property to that selector. In this case I have added <div>
because I have many divs with background images on this site.
This tip is from https://stackoverflow.com/questions/31908444/fix-for-blurry-images-on-browsers-used-by-a-mac-retina