SXGA- is a variant of the Super eXtended Graphics Array (SXGA) display resolution. SXGA refers to a resolution of 1280x1024 pixels with an aspect ratio of 5:4. Trying to display this resolution on a 4:3 monitor will yield bad results. To fill the gap is SXGA-, which has a resolution of 1280x960, for an aspect ratio of 4:3.
