If you're using a Mac, choose Macintosh. Give the file a name. A dialog box will appear. When saving in JPEG format, you can specify image quality and compression level for the file. Medium compression usually works well.
Baseline is standard and selected by default.
To optimize the color quality of the image, select Baseline Optimized. To save the file as a progressive JPEG, select Progressive. This option displays the image gradually as it is downloaded, using a series of scans to show increasingly detailed versions of the image. However, progressive JPEG images require more RAM for viewing and are not supported by all browsers. A dialog box will appear called Indexed Color.