Using the z-index CSS property, a property for layering content on pages.
At the top of their source before the actual page content starts, they've got a div at z-index: 999 which covers the whole content area, then the login appears at z-index: 1000. Any clicks outside the login box land on the other div, and not on the content below. When the div is hidden (as it is when you first visit the page) the page operates as expected.
At the top of their source before the actual page content starts, they've got a div at z-index: 999 which covers the whole content area, then the login appears at z-index: 1000. Any clicks outside the login box land on the other div, and not on the content below. When the div is hidden (as it is when you first visit the page) the page operates as expected.