The CSS (Cascading Style Sheets) style code (look at the page source), defines the default behavior of the P tag to use justification. Thus, all paragraphs in the page will be justified.

This paragraphs in this file are an example of the usage. The paragraphs are justified, meaning that tiny slivers of white space are added between words (and sometimes, between letters), so that the length of each line is the same number of pixels, resulting in left and right margins that are straight lines. It looks pretty nice when done correctly, but it can look bad if the paragraph is too short, so that the slivers of white space are big, not tiny.