Corrected typo in section 3.1 where seemingly a reference was made to category C instead of S.

Anonymous

]]>I have

touched the formatting of this ancient entry,

expanded and streamlined the Idea-section a little,

added illustrating diagrams for the definition of the sieves appearing in the definition (here) of local epis from a given site

added the version of the definition for covergages instead of Grothendieck topologies (here, is this in Johnstone?)

added statement of the proposition that the Cech nerve projection out of a local epi is a local weak equivalence of simplicial presheaves (here)