Darthatron apparently made this a while ago, but I figure it should be posted here for quick reference. Credit also goes to the wonderful FFTA Battle Mechanics Guide, seen on GameFAQs.
00 [Not Seen]
01 - None
02 [Not Seen]
03 - 100%H, Gadget, Inflict Protect
04 - 100%H, EqpSword, Inflict Disable
05 - 100%H, Gadget, Inflict Shell
06 - SType, Gadget, Inflict Blind
07 - 100%H, Gadget, 100% Heal
08 - SType, Gadget, Inflict Sleep
09 - 100%H, Gadget, Inflict Haste
0A - 100%H, Gadget, Dispel
0B - SType, Gadget, Inflict Poison
0C [Not Seen]
0D - SType, Gadget, Non-Undead: Inflict Doom
0E - 100%H, KOed Unit, Revive to Full HP
0F - 100%H, KOed Unit, Revive to 25% HP
10 [Not Seen]
11 - 100%H, Self, Draw Weapon
12 - 100%H, Self, [Eff1 Damage / 4] Damage
13 - 100%H, Self, Max HP Damage
14 - 100%H, Self, Caster's HP Damage
15 - 100%H, Self, Eff1Dep: [Eff1 Damage / 4] Damage
16 - 100%H, Self, Inflict Speed DOWN
17 - 100%H, Self, 100% Damage
18 - 100%H, Self, Eff1Dep: Heal Eff1 Damage
19 [Not Seen]
1A - 100%H, Self, Lose 30 Gil
1B - 100%H, Default, Eff1Dep: Delay Unit
1C - AType, Default, Delay Unit
1D - 100%H, Default, Inflict Quicken
1E - 100%H, Default, Inflict WAtk UP/WDef UP/MPow UP/MRes UP
1F - SType, Default, Doom Archer Effect*
20 - AType, Default, Matra Magic Effect*
21 - AType, Default, [(Target's HP + 1) * 0.9] Damage
22 - AType, Default, Steal 2 JP
23 - AType, Default, 100% Damage to MP, capped to Target's MP
24 - 100%H, Default, Heal 80 MP
25 - 100%H, Default, Inflict Astra
26 - 100%H, Default, Esuna
27 - SType, Default, Eff1Dep: Inflict Frog
28 - SType, Default, Inflict Frog
29 - 100%H, Default, Remove Frog
2A - 100%H, Cover Effect
2B - ---, Enemy, Aim: Wallet Effect*
2C - 100%H, Default, Inflict Advice
2D - 100%H, Default, Inflict Shell
2E - SType, Default, Elementalshift Effect*
2F - SType, Default, Eff1Dep: Inflict Stop
30 - SType, Default, Inflict Stop
31 - AType, Default, Inflict Speed DOWN
32 - AType, Default, 400% Damage
33 - 100%H, Default, (Target's Kills * 10) Damage
34 [Not Seen]
35 - 100%H, Default, 100% Damage
36 - 100%H, Default, 999 Damage
37 - 100%H, Default, Limit Glove Effect
38 - AType, Default, 30 Damage
39 - AType, Default, [(Target's HP + 1) / 2] Damage
3A - AType, Default, [Target's HP / 4] Damage
3B - AType, Default, Mutilate Effect*
3C - AType, Default, Goblin Punch Effect*
3D - AType, Default, Rand{2..12} Damage
3E - AType, NonUndead, (Caster's Max HP - Caster's HP) Damage
3F - AType, Default, 100% Damage
40 - AType, Default, 100% Damage, capped to Target's Max HP
41 - AType, Default, 50% Damage, 2.0x Hit Rate
42 - AType, Default, 200% Damage, 0.5x Hit Rate
43 - AType, Default, Throw Effect*
44 - SType, Default, Eff1Dep: Inflict Disable
45 - SType, Default, Inflict Disable
46 - 100%H, Default, Remove Disable
47 [Not Seen]
48 - SType, Default, Eff1Dep: Inflict Immobilize
49 - SType, Default, Inflict Immobilize
4A - 100%H, Default, Remove Immobilize
4B - 100%H, Default, Eff1Dep: Knockback
4C - SType, Default, Eff1Dep: Inflict Berserk
4D - SType, Default, Inflict Berserk
4E - 100%H, Default, Inflict Protect
4F - SType, Default, Hastebreak Effect*
50 - ---, Default, Aim: Vitals Effect*
51 - ---, Default, Acid Effect
52 - 100%H, Default, Inflict Reflect
53 - 100%H, Enemy, Detect Hidden Items
54 [Not Seen]
55 - SType, Default, Eff1Dep: Inflict Blind
56 - 100%H, Default, Eye2Eye: Inflict Blind
57 - SType, Default, Inflict Blind
58 - 100%H, Default, Remove Blind
59 - 100%H, Default, Heal to full HP
5A - 100%H, Default, Heal (Caster's HP) Damage
5B - 100%H, Default, 100% Heal
5C [Not Seen]
5D - SType, Default, Eff1Dep: Inflict Confusion
5E - 100%H, Default, Eye2Eye: Inflict Confusion
5F - SType, Default, Inflict Confusion
60 - SType, Default, Bad Breath Effect*
61 - SType, Default, Inflict Sleep
62 - SType, Default, Inflict Petrify
63 - 100%H, Default, Remove Petrify
64 - SType, Default, Inflict WDef DOWN/MRes DOWN
65 - AType, Default, Break Armor Effect
66 [Not Seen]
67 - SType, Default, Eff1Dep: Inflict Slow
68 - SType, Default, Inflict Slow
69 - 100%H, Default, Inflict Haste
6A - 100%H, Default, Dispel
6B - 100%H, Default, Soundwave Effect
6C - 100%H, Default, Inflict Expert Guard
6D [Not Seen]
6E - SType, Default, Eff1Dep: Inflict Silence
6F - SType, Default, Inflict Silence
70 - 100%H, Default, Remove Silence
71 - 100%H, Default, Hibernate Effect
72 - AType, Enemy, Steal JP
73 - AType, Enemy, Steal Gil Effect
74 - AType, Enemy, Steal EXP
75 - AType, Enemy, Steal Accessory
76 - AType, Enemy, Steal Armor
77 - AType, Enemy, Steal Helm
78 - AType, Enemy, Steal Shield
79 - AType, Enemy, Steal Weapon
7A - AType, Enemy, Steal Ability, 0.25x Hit Rate
7B - 100%H, Default, Inflict Conceal
7C - SType, Default, Eff1Dep: Inflict Poison
7D - SType, Default, Inflict Poison
7E - 100%H, Default, Remove Poison
7F - SType, Default, Inflict Zombie
80 - 100%H, Default, Remove Zombie
81 - ---, Default, Break Weapon Effect
82 - SType, Default, Inflict WAtk DOWN
83 - 100%H, Default, Inflict Boost
84 - SType, Default, Inflict Addle
85 - 100%H, Default, Inflict WDef UP
86 - AType, Default, Hurl Effect*
87 - 100%H, Default, Inflict Defense
88 - 100%H, Default, Eff1Dep: Inflict MPow DOWN
89 - SType, Default, Inflict MPow DOWN
8A - 100%H, Default, Inflict MRes UP
8B - 100%H, Default, Cureall Effect*
8C - SType, Enemy, Eff1Dep: Inflict Charm
8D [Not Seen]
8E - SType, Enemy, Inflict Charm
8F - 100%H, Default, Change Laws
90 - 100%H, NonUndead, SameLvDigit: 100% Damage
91 - 100%H, Undead, SameLvDigit: 100% Heal
92 - 100%H, LvlDivBy3, Inflict WDef DOWN
93 - 100%H, LvlDivBy3, Inflict MRes DOWN
94 - 100%H, NonUndead, LvlDivBy5: Inflict KO
95 - 100%H, Undead, LvlDivBy5: Heal to full HP
96 - 100%H, SmeLvlDay, 100% Damage
97 - 100%H, Enemy, 100% Damage to MP
98 - 100%H, Enemy, Eff1Dep: 100% Damage
99 - 100%H, Enemy, 100% Damage
9A - AType, Enemy, 100% Damage
9B - SType, Enemy, Inflict Berserk
9C - ---, Enemy, Drop Weapon
9D - ---, Parley Effect*
9E [Not Seen]
9F - AType, NotSelf, (Caster's HP) Damage
A0 - AType, NotSelf, 100% Damage
A1 - SType, NotSelf, Inflict Sleep
A2 - 100%H, NonUndead, Heal to full MP
A3 - 100%H, NonUndead, Esuna
A4 - AType, NonUndead, 100% Damage
A5 - 100%H, NonUndead, Inflict Regen
A6 - 100%H, NonUndead, Inflict Auto-Life
A7 - 100%H, NonUndead, Heal to full HP
A8 - 100%H, NonUndead, 100% Heal
A9 - SType, NonUndead, Eff2Dep: Inflict Confuse
AA - SType, NonUndead, Inflict Doom
AB - SType, NonUndead, Eff1Dep: Inflict Doom
AC - 100%H, NonUndead, Inflict KO
AD - SType, NonUndead, Inflict KO
AE [Not Seen]
AF - AType, NonAnimal, 100% Damage
B0 - ---, NonAnimal, Break Weapon Effect
B1 - AType, NonDragon, 100% Damage
B2 - 100%H, Undead, (Target's Max HP) Damage
B3 [Not Seen]
B4 - AType, Undead, 100% Damage
B5 - 100%H, Undead, Heal to full HP
B6 - 100%H, Undead, 100% Heal
B7 - SType, Undead, Remove Unit, 0.5x Hit Rate
B8 [Not Seen]
B9 - AType, Animal, 100% Damage
BA - AType, Animal, 200% Damage
BB - ---, Animal, Parley Effect*
BC - SType, Animal, Inflict Addle
BD - ---, Animal, Capture Effect*
BE - AType, Dragon, 200% Damage
BF - ---, Dragon, Parley Effect*
C0 - AType, Enemy, Mug Effect
C1 - ---, Control Effect
C2 - ---, Friend Effect*
C3 - 100%H, NonUndead, Inflict Regen
C4 - 100%H, Undead, Heal (Caster's Max HP - Caster's HP) Damage
C5 - AType, Default, 200% Damage
C6 - AType, Default, 50% Damage
C7 - AType, Default, 300% Damage
C8 - 100%H, Default, Morph Effect
C9 - SType, Enemy, Inflict Sleep
CA - 100%H, Default, 50% Damage
CB - 100%H, Judge, Stop Judge
CC - SType, Default, Inflict Disable/Immobilize
CD - 100%H, Default, Give JP
CE - 100%H, Default, Remove Yellow Card
CF - 100%H, Default, Add Yellow Card
D0 - 100%H, Default, Eff1Dep: Steal 2 JP
Good job man.
Do you guys know which byte these effects refers to?
I will recommend that you should travel to the FFTA Skill Spreadsheet topic as it covers the majority of topics in this area. To answer your question, there can be a maximum of 4 effects on an ability. Those 4 effects are mapped to bytes 0x0C -> 0x0F for each skill.