I have recently analyzed several web pages for Dreamweaver customers that complained about slow page loading times. A trend that I have noticed is images used for tiling backgrounds with a width or height of 1 pixel. I have even seen some 1×1 images used for tiling. Yikes!
“Tiling” refers to using a CSS background image that repeats in the X and/or Y directions to fill a page or element.
While it’s generally best to make images as small as possible, one exception to that rule is for tiling images. The smallest download that browsers can do is 1K bytes, so the best size for tiling image files that can be made to be under 1K in size is “as close to 1K without going over”. This can significantly reduce the amount of tiling that Dreamweaver and browsers need to do, which improves page loading performance.
For example, consider a 1×1 image versus an equivalent 10×10 image. The size of both images is under 1K, so the download time is the same, but the smaller image is tiled up to 100 times more than the larger image, which requires more time to render.
This argument also applies to non-tiled images, but those can easily be combined in a single file using the CSS Sprite technique.