Soldato
As far as I was aware, the order in which they are listed in the game is the chronological order of events (ie you escape one level in a car, and the beginning of the next level shows the car out of gas and you having to leave it )
I haven't given the names of the levels above as don't want to give away any spoilers, however I don't really think that applies in either of the L4D games
I haven't given the names of the levels above as don't want to give away any spoilers, however I don't really think that applies in either of the L4D games