When asking about sizing an ASP.net background image I received the following advice from an expert. Hoe do I "make the background slice repeat only in the x-direction."
There is no "standard ASP.net background" but there are a large variety of monitor sizes. For a gradient background, you normally make it a narrow slice, just a few pixels wide, by the tallest screen size you expect to see. I normally would make the background color the same as the bottom end of the gradient and make the background slice repeat only in the x-direction. That way, if the screen is taller than the gradient, the background will match the bottom of the gradient and make it look like there is no discontinuity at the bottom.