Fluid, Elastic, Fantastic!
A fundamental question when creating web pages is whether the layout will have a fixed width or whether it will be able to expand and contract depending on factors such as the width of the browser window (or viewport). Fixed-width, pixel-based layouts are predictable but not very adaptable to changing browser conditions. Fluid (or liquid) layouts—even with a minimum and maximum width set—are harder to control, especially if the design requires features like a full-width header image. Em-based designs—especially when combined with some fluid elements—in a sense combine the both of best worlds…
