[1] CSS3 Generated and Replaced Content Module ( (5/15/2003, 12:54:58 PM 版)) <http://www.w3.org/TR/2003/WD-css3-content-20030514/#line-markers>
[2] CSS Generated Content Module Level 3 ( (4/20/2011, 5:28:30 PM 版)) <http://dev.w3.org/csswg/css3-content/#line-markers-the-line-marker-pseudo-elem>
Google search: ::line-marker