In the CCG Magic:The Gathering, there exists a ruling body (also known as the DCI) from which all tournament formats come. Currently there are 5 Major Constructed Tournament Formats.

Classic or Type 1
Classic Restricted or Type 1.5
Block, currently known as MBC or Mirrodin Block Constructed
Extended or Type 1.x (aka what this writeup is about)


Extended Legal Decks can be composed of cards from any of the following basic editions and expansions
Sixth Edition
Seventh Edition
Eighth Edition

Tempest
Stronghold
Exodus
Urza's Saga
Urza's Legacy
Urza's Destiny
Mercadian Masques
Nemesis
Prophecy
Invasion
Planeshift
Apocalyse
Odyssey
Torment
Judgement
Onslaught
Legions
Scourge
Mirrodin as of Oct. 20th, 2003


This means that cards from
Limited Edition (aka Alpha and Beta)
Unlimited Edition
Revised Edition
Fourth Edition
Fifth Edition
Chronicles (which is considered part of Fourth Edition)
Arabian Nights
Antiquities
Legends
The Dark
Fallen Empires
Ice Age
Alliances
Mirage
Visions
Weatherlight
are legal only if they also appear reprinted in a newer set.

The following cards are explicitly banned in this format even though they are in legal sets:

Dark Ritual
Dream Halls
Earthcraft
Entomb
Frantic Search
Goblin Lackey
Lotus Petal
Memory Jar
Mind Over Matter
Replenish
Survival of the Fittest
Time Spiral
Tolarian Academy
Windfall
Yawgmoth's Bargain
Yawgmoth's Will


After Pro Tour New Orleans (Oct. 31-Nov.2 2003) the DCI will probably be banning some more cards from the format due to such overpowered cards like Chrome Mox, Tinker and Goblin Charbelcher.