PSA: Don't save JPEGs as JPEGs

Whenever you find a jpeg/jpg image on the internet worthy of saving, DO NOT save it as a JPG. Save it as PNG file or another lossless format, like RAW, TIFF, or BMP.
This should be common knowledge, but every time you save a JPEG as JPEG, the compression process is performed again which has the chance of introducing more artifacts and errors. This re-saving, along with the other cancerous plague of reposting old images(don't do this either), have the net result of reducing once beautiful images to husks of their former selves. This is especially horrific to witness when dealing with high resolution wallpaper images. While saving an image to a different format won't undo any damage that has already occurred, it will preserve the image in its current state from further degradation.

Note that this only occurs when you right click an image and hit the "Save As" option, or something along those lines. Directly downloading an image from a hosting site or as part of an archive is fine.

For more information --> http://www.scantips.com/basics9jb.html

Yes, several sites have made the argument that the degradation is often too minute to be noticed, but that doesn't change the fact that it happens. By continuing to re-save as JPG you are propagating the spread of entropy, and going against the will of the Lord Kelvin.