If you look at http://www.gocomics.com/foxtrot , you will see that they have uploaded a full-resolution TIFF version of the comic (7680x5400) instead of the Web-resolution JPEG version. Your browser will probably refuse to display it, so right click on the displayed Alt text and View Image to download it. It's a 3.75 MB file.
This will likely be fixed by the time you read this message.
Oddly enough, there are some resizing artifacts, as if someone had used Nearest Neighbor sampling at some point when processing the image.
Screenshot available at: http://i.imgur.com/tSY4o.png