Every doodad on a web page is useful to somebody sometimes, but usually they're just clutter. This style hides the header, footer, and sidebars (and all their doodads) by reducing them to thin placeholders at the top, bottom, and left edge of the screen, and expands them again when you mouse over a placeholder. The Save/Share/Font toolbar isn't auto-hidden, but it's been moved from above the article text to below it.

Nothing is removed from a page, only hidden at one of the edges of the screen. (Out of sight!)