Selectors - CSS Reference - page 87

Name
::first-line
Generates:
A pseudo-element that contains the first formatted line of an element
Description:
This is used to style the first line of text in an element, regardless of how many or how few
words may appear in that line. :first-line can be attached only to block-level elements.
There is a limited set of properties that can apply to a first line.
Example:
p.lead:first-line {font-weight: bold;}