There are two approaches to saving a photo in Photoshop, with each having a certain purpose.
One way is to use the standard Save As, another is a special feature in Photoshop called Save for Web & Devices… which is often used to save your photos when preparing for publication to the Web.
Save as: Make use of this method when saving your photo for archiving or if you are planning to work on it later. We recommend saving the file type as a Photoshop or .PSD file, which will also save extra Photoshop-specific information about your photo.
Save for Web & Devices: Use this when you are ready to export your photo for publication to the Web. While it’s possible to save a photo with the regular “save as…” option and still publish it to the Web, the Photoshop built-in “Save for Web” feature specifically prepares your photo for the Web and has added features that allow you to see how it will appear once it’s on a Web site. This ensures your photos will show up properly on the internet.
Saving a Picture for Web Use – Photoshop CS4 – Photo Editing Basic Part 8
YouTube - Photo Editing Basics Part 8 - Saving a Picture for Web Use
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