Mouse OpeRation 3ple Clicking

Double clicking refers to clicking (and, naturally, releasing) a button (often the primary one) twice. Software recognizes both clicks, and if the second occurs within a short time, the action is recognized as a double click.
If the second click is made after the time expires it is considered to be a new, single click. Most modern operating systems and mice drivers allow a user to change the speed of a double click, along with an easy way to test the setting. Some software recognize three or more clicks (triple click), such as progressively selecting a word, sentence, or paragraph in a word processor text page as more clicks are given in a sequence.

Triple clicking in Safari highlights the whole line, including the line break at the end. Firefox stops short of the line break.