Server.properties

Server.properties is the file which stores all the settings for a multiplayer (Minecraft or Minecraft Classic) server.

If you are going to edit server.properties it is important that you use the same structure as the original uses, although the order of the lines is arbitrary. The text before the equal sign is the key, which you shouldn't change. The text after the equal sign is the property's value, which you can edit. Lines that begin with  are comments - altering or removing these lines has no effect on the game.

After changes are made to the server.properties file, the server must be restarted for them to take effect.

If the server.properties file does not list all properties (such as if a new version of the server adds new properties, or if the file does not exist), then on startup the server will rewrite the server.properties file with the new properties listed and set them to their default values.

File Location
This file is automatically generated upon first start of the server (if it doesn't exist).

Server.properties
As of 1.1, these are the default settings for a newly installed Minecraft server: allow-nether=true level-name=world enable-query=false allow-flight=false server-port=25565 level-type=DEFAULT enable-rcon=false level-seed= server-ip= spawn-npcs=true white-list=false spawn-animals=true online-mode=true pvp=true difficulty=1 gamemode=0 max-players=20 spawn-monsters=true generate-structures=true view-distance=10 motd=A Minecraft Server
 * 1) Minecraft server properties
 * 2) Date and time of creation of file

Other Features
In 1.8, having spawn-monsters=false & difficulty=1 will allow mobs to spawn from spawners and do not instantly disappear. Mob will not spawn just because it is dark. Unconfirmed bug or feature.

Server.properties