davist11/In-Field-Labels-jQuery-Plugin — comment on commit 04756412fd3fba6d9f6e15e666970fe206d4dcb0
File: src/jquery.infieldlabel.js line 37
By streetpc:

Pro: no need of immediate `position: relative` ancestor.
Cons: relying only on this this positioning will break if any vertical modification comes between the beginning of the "closest positioned parent" and the field.
Example: http://jsfiddle.net/7BgEy/