ah, good point, "Our #callout element is set to position: absolute, and since its parent element, #content is set to relative, the offset properties we’re using

ah, good point, "Our #callout element is set to position: absolute, and since its parent element, #content is set to relative, the offset properties we’re using on #callout are based off the coordinates created by #content." would be nice to see it called out as one of the core techniques above though. or I guess I could have just read the whole article before commenting :)