________ are useful to alert the user that an action has been completed, but message boxes could also be used for custom error messages

What are the guidelines used when creating Web pages for input?

What will be an ideal response?

Instead of using _____ elements to place images from a sprite sheet, developers set the sprite sheet graphic as the background for a div or other block element, then set properties for the div that show only the relevant part of the sprite sheet as the background.

Fill in the blank(s) with the appropriate word(s).