File Size
Working with Photoshop means working with large files; manipulating those files increases their sizes considerably. Therefore managing file size is critical, as it affects the performance of the computer, the storage options, and most importantly for significant number of IC users, the space it occupies on the screen. File size can by cut by first reducing the file resolution to fit the output medium (print, email, web..); second by reducing the pixels dimension; third by changing the file format, which is the final step before the image is ready to be exported. For the image to fit within the screen, the pixel dimension should be less than the pixel dimension of the monitor ( 800×600 for a standard 15 inch monitor screen, 1152×864 for IC monitors).

Work from a copy of the image!
Always advise customers to do this. That way if you cannot undo a mistake, you have the original to go back to and make another copy! Missteps? Mistakes?

Three ways to undo:
Edit > Undo
Edit > Step backward
Alternatively, use the History palette to undo one or multiple changes at once.

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