It happened to me once when reading a FAQ for rootnode support IRC channel. There was a most important "point 0" in FAQ, that was emphasized by moving it above the page header. It was supposed to be the very first thing visitor will read, but my mind didn't even register this text being there (even after being told that there
is a "point 0" and revisiting the page). Needless to say, I got into some trouble because of that, but I managed to convince FAQ maintainers that banner blindness[1] is a real thing, and they fixed the FAQ.
http://en.wikipedia.org/wiki/Banner_blindness